I haven't been active on this site yet, but I am active on other internet conlang sites (like the Conlang Bulletin Board, Zompist Bulletin Board, and Conlang Mailing List) and I'm surprised at the description in the original post. (That said, I don't have experience maintaining threads about conlangs of my own on these sites.) My answer here is mainly based on my perspective about what I've seen on these other sites.
My experience is that, at least for many people, pushback is strongest against advocacy of auxiliary languages. Yes, many people on these sites are more interested in "naturalistic" conlangs, but I think there are definitely people who would be interested in discussing linguistic aspects of auxililary languages and engineered languages. (For example, the Conlang Mailing List has seen a fair number of posts by the creators of engineered, non-naturalistic constructed languages.)
An issue that often seems to come up is that the set of people who are interested in posting about auxiliary languages overlaps significantly with the set of people who are interested in promoting auxiliary languages. It is tiresome when people who think they've come up with the next Esperanto make posts arguing about why their language is the greatest, especially if it's obvious that the poster hasn't taken much time to study linguistics or the alternative existing auxiliary languages that already exist.
I think the Stack Exchange model of questions and answers is inherently more hostile to advocacy efforts than the bulletin-board or mailing-list discussion paradigms, so I wouldn't think that would be as big a problem on this site, and I expect that there should accordingly be less hostility towards on-topic posts about auxiliary languages and engineered languages here. None of these subjects seem inherently off-topic for a site about constructed languages.