As opposed to "If only we had better background checks" or "If only we banned assault weapons", right? Cause that's not speculative at all.
That would be discussing macro changes and supported with stats from other nations, etc.
As opposed to the stats showing the massive statistical death rate difference based on whether civilians intervene in a shooting before police arrive or not.
It doesn't involve taking singular events and making up your own narrative about what everyone did, what they were thinking and the rest of it.
Except that this isn't the one singular event which shows this pattern. If it was, you'd have a point. This one is just an example of the pattern we see in shootings where civilians intervene. We're both speculating about what might have happened in that one case if things had happened differently, but while I'm speculating that it followed the pattern (when civilians intervene shooters stop shooting random people), while you're speculating that this was the exception (that the shooters actions had nothing to do with the civilian intervention).
We could also speculate that in the dozens of cases where civilians intervened in shootings that their intervention had nothing to do with the ultimate outcome, but the statistics quite clearly show a massive difference in body count. We must conclude that at least in some of those cases, the intervention did in fact affect the outcome. Again, it's not about just one instance of a shooting, but a trend that is quite consistent across a whole set of them.
Again, that seems hypocritical.
"If I'm not allowed to make up what a shooter was thinking, you're not allowed to discuss potential benefits of legislation"? Well, any port in a storm.
It's not about what a specific shooter was thinking, but about how his actions changed based on the conditions around him. You are also speculating about the changes potential shooters might make based on a given piece of legislation. You're assuming that if we pass law X, shooters will just say "Aw shucks. Guess I can't go on my rampage". But again, there's zero evidence to support your assumption, while there's a mountain to support mine.