the study was intending to measure the rate of suicidal thoughts among transgender people.

Seems like a great way to get a lot of datapoints is to use a transgender forum. Seems like a great way to measure suicidal thoughts is to ask "do you have suicidal thoughts"

So seems like a great approach to gather a lot of evidence for the question at hand?

Seems like you just don't like the evidence because it doesn't reach the rather bigoted conclusion you want it to