There exist online communities on secular websites, to discuss religion-related topics such as the bible, that largely consist of Christians and their contributions. Some of those Christians use the platform afforded to them to make truth claims that of course conflict with Jewish belief, and in some cases these websites and their communities may be de facto advancing the Christian message despite the secular nature of the company running the site.
If this is judged to be the case would it be asur for a Jew to participate in any way, as:
being an active or semi-active user on the site is a gift even if their views are opposed, because it could promote the site (eg by making it rank higher in Google).
People up to no good may come and learn from what is said, so inadvertently their religion may be promoted by the Jewish participation.
There are related, narrower, questions here and here, neither of which has any answers from Jewish members of the community (possibly because the questions are localized). I'm very much hoping to attract answers to the broader question here to understand the Jewish perspective or spectrum thereof.