It might be helpful if they argued why you should join one of their sects and give a positive reason to switch. If all they do is downplay Mormons, then what alternative are they giving?
Me for instance. I am a CHRISTIAN. It is unimportant which denomination of church I worship at, as long as it teaches the bible and only the bible.
I beleive you will find, if you look, that most if not all of the so-called "anti-mormons" are the same. They are not "pushing their own sect", they want Mormons (and everyone really)to escape from the sect/cult they are trapped in.