He's going to make another batch of ice cream.
If he were frugal he wouldn't. That's kind of the point of frugality.
You're using an incredibly restrictive definition of frugal. Frugality isn't about total money spent, but about spending the least amount for what you get (not being wasteful). It's about "bang for buck". If you spend $10 on supplies to make one batch of ice cream and screw it up, you've spent $10 for zero result. If you buy a second $10 worth of supplies and make a batch of ice cream, you've gotten one batch for $20. Assuming your objective was to have a batch of ice cream, the second option is actually more frugal than the first.
As you make more successful batches the relative "cost" of failing with the first decreases. Obviously, this doesn't mean you rush out to buy a hundred batches of ice cream, but if we're assuming that the family would make several batches over a period of time anyway, then this isn't costing more money than they would have spent anyway. Given this situation, if one family member (like the father) who is willing to sacrifice flavor for cost, keeps the bad batch in the freezer and puts that in his bowl while providing new/good ice cream to the rest of the family, then he's able to sit with his family with all of them eating ice cream together, while making up for the loss of the initial batch.
Net effect is that he regains the lost cost of the first batch. Obviously, he could do the same thing by just not eating ice cream, but if this was more of a social thing for the family, he might choose the course he did. Either way, it's still an example of frugality. He choose not to waste something which was (presumably) still edible and thus fulfilled the purpose of ice cream (it's cold), but just didn't taste great. He did so in a way that protected his family from the cost of the initial mistake (they weren't forced to either eat bad tasting ice cream or go without).
Why is this a problem? Why is this such a horrible thing that he and his entire family should be mocked for it?
To me, the response is a pretty glaring example of partisanship gone to nutty ends.
going to ridiculous lengths to defend your assumption, so I guess we could give you this one.
I'm responding to people attacking someone for relating an amusing story about their grandfather. But it's my motives that should be questioned instead?