And many would not? Do people who don't like religious institutions have an obligation to be more respectful than the average person or else their arguments are invalid?

I think they have exactly the same obligation to be respectful. I'm religious, but if this had been a thread about an atheist dating site I wouldn't have commented like you did, and if another religious person did I'd have been just as critical of them.

You are correct many would not, but you get to choose what group you emulate. Personally I'd prefer to be respectful where possible.

And no being disrespectful doesn't invalidate your argument. But it does cause division, something you didn't seem to want.