Oh, second comment: your framing is disengenuine.

These are scientists, I'm a scientist, we're held to standards of peer review and methodological scrutiny.

I don't need to establish how and whether we're doing science with authority-- that's the beauty of the invention of the scientific method. I also don't need to establish whether these are facts or opinions, because the body of research is so large and well-discussed, for decades now, that peer review has had plenty of time to do it's work.

To humor you-- the methods used have been all of the above: surveys, experiments, studies, etc.

To humble you-- it's extremely arrogant of you to ask a scientist, to their face, whether their research is real or just opinion. If you think all the research in this field is wrong, you can fix it the way we fix all our science: by conducting your own research and subjecting it to review by other experts in the field.