I suppose actors have as much right to speak up on an issue as everyone else, and we have the right to not take them seriously.
I mostly blame Twitter for this. Not too long ago most actors had their public appearances carefully curated, and they'd mostly just do interviews to promote their latest fillum. A minority were politically active - say Warren Beatty or Susan Sarandon on the left, or Charlton Heston or Clint Eastwood on the right, or Richard Gere with his Tibet activism - but they were usually serious and well informed about their subjects.
I also blame Bill Clinton, because on general principle he's responsible for lots of what's wrong with the world, but his lash up with Harvey Weinstein to make Hollywood an arm of the Democratic Party has had the effect of turning people like George Clooney into fairly serious power brokers.
So now we have actors who are on social media all fucking day and telling us their opinions on every subject that catches their eye, and confirming that most of them are idiots who only have jobs because they're good looking and have a talent for pretending.
Actors who acquire trans children like they acquire purse puppies are just another part of that idiocy.