Pointing to an ENTIRE CHAPTER OF US CODE is NOT AT ALL SPECIFIC. It's akin to saying "I know where Waldo is!" and pointing to a sea of millions of people dressed in peppermint striped shirts and hats. Sure, in general, you may be on track, but it's not at all helpful. Which tax "benefit" would you like to discuss, specifically?
You get that US legal code doesn't come in separate paragraphs, right? You asked for the "exact US code which grants these benefits per your argument". Did you even click the link and read? As I already explained, the code isn't written with just "stuff that marriage does". It's divided into "stuff that affects tax rates, including marriage" and "stuff that affects social security, including marriage". I have provided you exactly that which you asked for.
Do you want me to quote just the parts that reference marriage? You'll lose formatting and links in the text, but here you go:
a) Married individuals filing joint returns and surviving spouses
There is hereby imposed on the taxable income of—
(1) every married individual (as defined in section 7703) who makes a single return jointly with his spouse under section 6013, and
(2) every surviving spouse (as defined in section 2 (a)),
a tax determined in accordance with the following table:
If taxable income is: The tax is:
Not over $36,900 15% of taxable income.
Over $36,900 but not over $89,150 $5,535, plus 28% of the excess over $36,900.
Over $89,150 but not over $140,000 $20,165, plus 31% of the excess over $89,150.
Over $140,000 but not over $250,000 $35,928.50, plus 36% of the excess over $140,000.
Over $250,000 $75,528.50, plus 39.6% of the excess over $250,000.
d) Married individuals filing separate returns
There is hereby imposed on the taxable income of every married individual (as defined in section 7703) who does not make a single return jointly with his spouse under section 6013, a tax determined in accordance with the following table:
If taxable income is: The tax is:
Not over $18,450 15% of taxable income.
Over $18,450 but not over $44,575 $2,767.50, plus 28% of the excess over $18,450.
Over $44,575 but not over $70,000 $10,082.50, plus 31% of the excess over $44,575.
Over $70,000 but not over $125,000 $17,964.25, plus 36% of the excess over $70,000.
Over $125,000 $37,764.25, plus 39.6% of the excess over $125,000.
(f) Phaseout of marriage penalty in 15-percent bracket; adjustments in tax tables so that inflation will not result in tax increases
(1) In general
Not later than December 15 of 1993, and each subsequent calendar year, the Secretary shall prescribe tables which shall apply in lieu of the tables contained in subsections (a), (b), (c), (d), and (e) with respect to taxable years beginning in the succeeding calendar year.
(2) Method of prescribing tables
The table which under paragraph (1) is to apply in lieu of the table contained in subsection (a), (b), (c), (d), or (e), as the case may be, with respect to taxable years beginning in any calendar year shall be prescribed—
(A) except as provided in paragraph (8), by increasing the minimum and maximum dollar amounts for each rate bracket for which a tax is imposed under such table by the cost-of-living adjustment for such calendar year,
(B) by not changing the rate applicable to any rate bracket as adjusted under subparagraph (A), and
(C) by adjusting the amounts setting forth the tax to the extent necessary to reflect the adjustments in the rate brackets.
(3) Cost-of-living adjustment
For purposes of paragraph (2), the cost-of-living adjustment for any calendar year is the percentage (if any) by which—
(A) the CPI for the preceding calendar year, exceeds
(B) the CPI for the calendar year 1992.
(4) CPI for any calendar year
For purposes of paragraph (3), the CPI for any calendar year is the average of the Consumer Price Index as of the close of the 12-month period ending on August 31 of such calendar year.
(5) Consumer Price Index
For purposes of paragraph (4), the term “Consumer Price Index” means the last Consumer Price Index for all-urban consumers published by the Department of Labor. For purposes of the preceding sentence, the revision of the Consumer Price Index which is most consistent with the Consumer Price Index for calendar year 1986 shall be used.
(A) In general
If any increase determined under paragraph (2)(A), section 63 (c)(4), section 68(b)(2) or section 151 (d)(4) is not a multiple of $50, such increase shall be rounded to the next lowest multiple of $50.
(B) Table for married individuals filing separately
In the case of a married individual filing a separate return, subparagraph (A) (other than with respect to sections 63 (c)(4) and 151 (d)(4)(A)) shall be applied by substituting “$25” for “$50” each place it appears.
(7) Special rule for certain brackets
(A) Calendar year 1994
In prescribing the tables under paragraph (1) which apply with respect to taxable years beginning in calendar year 1994, the Secretary shall make no adjustment to the dollar amounts at which the 36 percent rate bracket begins or at which the 39.6 percent rate begins under any table contained in subsection (a), (b), (c), (d), or (e).
(B) Later calendar years
In prescribing tables under paragraph (1) which apply with respect to taxable years beginning in a calendar year after 1994, the cost-of-living adjustment used in making adjustments to the dollar amounts referred to in subparagraph (A) shall be determined under paragraph (3) by substituting “1993” for “1992”.
(8) Elimination of marriage penalty in 15-percent bracket
With respect to taxable years beginning after December 31, 2003, in prescribing the tables under paragraph (1)—
(A) the maximum taxable income in the 15-percent rate bracket in the table contained in subsection (a) (and the minimum taxable income in the next higher taxable income bracket in such table) shall be 200 percent of the maximum taxable income in the 15-percent rate bracket in the table contained in subsection (c) (after any other adjustment under this subsection), and
(B) the comparable taxable income amounts in the table contained in subsection (d) shall be 1/2 of the amounts determined under subparagraph (A).
(5) Special rules for determining parent to whom subsection applies
For purposes of this subsection, the parent whose taxable income shall be taken into account shall be—
(A) in the case of parents who are not married (within the meaning of section 7703), the custodial parent (within the meaning of section 152(e)) of the child, and
(B) in the case of married individuals filing separately, the individual with the greater taxable income.
There. That's every part either specific to, or that references, marriage in this section of the US legal code. I've given you plenty to work with, now you go get to finding those primary sources explaining exactly why the tax brackets are different and there's a whole section on phasing out the marriage penalty, and why there's a special mention of married and unmarried folks in the section on "(g) Certain unearned income of children taxed as if parent’s income ".
As I said earlier: Knock yourself out. Have fun storming the castle!
Remember that this is precisely what you have demanded that I must do in order to defend my position. I think it's ridiculous, but by all means prove me wrong if you can.