OK:
#1 is wrong, because you don't have to be building a SFF system to use a mATX motherboard.
#2 is wrong, because you don't have to be on a budget to use an mATX board. There are some very expensive mATX boards, and some very cheap ATX boards.
#3 is wrong, because onboard video has nothing to do with anything. mATX boards can use whatever video card you put into it, if you want to do that. And ATX boards with onboard video use the same chipsets as mATX.
Your "can have" statements are wrong too, because mATX boards "can have" better features than an ATX board. It all depends on which one you are talking about
So as you can see, your fail was justified

Stop being so butthurt over it.