When approaching a topic regarding a marginalized group, heuristics like "mainstream" show their failure points. "Mainstream" is effectively asking for the opinion of non-marginalized people on the marginalized. This doesn't mean it's necessarily biased, but it has the tendency to be more biased.

However, there's an easy fix. The obvious correction to the heuristic is to in turn ask the marginalized group their opinion. In this case, that would mean asking one or more transwoman their opinion on the topic.