I do not see a problem in a member answering the question and then politely suggesting they try to upgrade the size of the tank. Like you said, there are a lot of differing opinions, and there is nothing wrong with that. How we express them if what matters. I'm sure most of us are guilty of losing patience or coming on too strong sometimes.
Something that stands out in my mind; this is a Betta fish care forum. So naturally aspects of betta fish care will be discussed and debated. It is all about being understanding and respectful of other opinions but also realizing you cannot make anyone take your own.
Regarding the other forum that said you were abusing your fish for not being in a 5 gallon: I know which one you are talking about, it is actually the first fish forum I ever joined. I can guarantee they are not that way anymore. I've seen you mention it a few times. I don't think it is fair to hold one discretion with a Mod against them forever. Just my 2 cents though.
Erika | Betta Fish Advocate