I think this thread is really a subset of a more general discussion of good posting etiquette.
I think it is perfectly appropriate to provide an opposing opinion on the merits of a particular aircraft. What is not appropriate is to post that opinion in a manner that implies that poster expressing a positive opinion is a less accomplished aviator because of that opinion.
There are certain posts that I think definitely cross that line.
The same applies to the type of flying one does. I like formation and aerobatics but that does not mean I should disparage others who don't want to do that type of flying.
A variety of opinions make the site more interesting and ultimately more valuable. Chasing away those deemed to be unworthy due to their aeronautical preferences is not in pprunes best interests.
BTW the first airplane I owned was a Cessna 150. I taught my wife how to fly in it and enjoyed 4 years of cheap fun flying. I only sold it so that I could join a floatplane syndicate.