How do you know if they're not really transgender anyway?
It's a general word that people who experience it probably need some documentation they are treated for gender dysphoria rather than take their word for it.
Transgender for me is more about gender dysphoria and people who wish they were another gender and so on and so forth. But a man in a dress looking to attack women from it like in that article, and so on and so forth... it's unlikely they ever really had what I see as the spirit of transgenderism.
And though it may require some mental gymnastics, I don't think saying that you'll revoke someone's identity card for bad behavior like the people in those articles is out of the question. If I'm a Democrat, and I strongly support racism, I'd expect some people not to see me as a Democrat any more. Just keep it fair and aim for the best rather than degrading people when you don't see them as X identity for certain reasons.
As for how I know about transgender people.... well I have been on HRT before and now identify as nonbinary. You don't really need a degree to try to spot some of your own, but others who are not, might.