Regardless of your stance on what is going on in Gaza, I don’t think unions should be picking a side either way.
The point of a union is to represent the worker toward their employer. This is most effective if all workers stand together.
Taking a stance on a matter that is so politically controversial as the situation in Gaza/Israel, only serves to divide workers, reducing the effectiveness of unions to achieve their core purpose.
If individuals (or groups of individuals) want to support or denounce either Israel or Palestine that should be their choice, but I don’t think a union should get involved in that.