I think a lot of the fights around THAC0 can be summed up thus:
1. THAC0 is harder than ascending AC vs “no it isn’t.”
Problem: “Harder” is a subjective judgement, and those that disagree with the sentiment above hear it and argue it is not true (because in their opinion, it is not). Those that agree hear those arguing against it and hear “you are dumb” or “maths is easy” and argue against those points. Often the argument seems to degenerate into “it is hard” vs “no it is not.” I think the fact that thousands of early players learned and used it disproves the conjecture that it is “hard” (this is a very different argument than “it is harder”).
Neither side is actually talking to the other one, because they are making two different arguments, all based around a subjective statement that cannot be proven true in all cases. For some, subtraction IS perceived as harder than addition. For others, it is not. You cannot convince the other side to come to see things your way, because it does not fit with their reality.
2. It may be fruitful to posit, “more people find descending AC to be harder than ascending AC.” This is not a statement of opinion, but a statement that can be empirically verified. Unfortunately I don’t know of any studies about this that verify or disprove it, but I my intuition is that this seems likely to be the case, given in most beginning maths textbooks, “addition” is taught after “counting” and “subtraction” is taught after “addition.” Since math as a discipline generally teaches more complex principles by adding them on top of simpler principles already taught, it seems that one might reasonably assume this ordering is evidence (not proof) that addition is usually seen as easier to learn than subtraction.
So I will posit the following are things we ought to all accept as probably true based on implicit evidence until explicit proof or disproof can be found:
1. Neither ascending nor descending AC is “better” for everyone. (“Better” is a subjective judgment).
2. Both are mathematically equivalent (I don’t think this is in dispute, but may as well put it out there).
3. Ascending AC is generally easier for most players to learn and use (based on both “addition” being taught before subtraction and the indirect evidence of nearly all systems shifting toward it over time).
I would venture to say, “insulting those who hold a different opinion on which is better” by way of insults such as “bad at math” or “THAC0 the clown” is unproductive.
Try not to offend other people. When you are other people, don’t try to be offended.
I grew up with THAC0. I can use it, I can speak it fluently. That doesn’t make be better or smarter than those that didn’t. I thought the idea of “THAC0 the clown” was funny because I had seen others struggle with the system (including in the days where there was no Ascending AC) and didn’t take its use as calling me a clown. I see it kind of like the French vs English language dichotomy in Canada. Quite a few know a French (THAC0), even more know English, most people that care to be are conversant in both, and those that don’t care to be tend to think their chosen language is “superior” despite both being perfectly functional languages for communicating ideas. These arguments all strike me as kind of silly, in the same way I think Quebecois that know English but pretend to only speak French (or those that know French but pretend to speak only English) are silly.
If you speak both BAB and THAC0, more power to you. Just please make sure you match the language of whomever you are speaking with instead of being a jerk and demanding everyone use your “preferred” language. Likewise, if you only speak one, you may expect when someone is speaking specifically to you that decorum would demand speaking the language you know, but don’t jump into a conversation they are having with those that speak the other language and demand they switch to yours (that group of gamers playing 1e that speak THAC0? Don’t rush in and demand they convert to BAB and vice versa for 5e gamers).
