As far as I know, they don't support Hamas. They support ordinary Palestinians. However, since Islamic extremists who support Hamas have also joined the movement, I suppose that's why you think that.
That's the same as saying there are Zionists among those who criticize Hamas.
There are people on both sides who cannot understand these nuances, and the OP is one of them. You guys oversimplify things, and extremism arises from this kind of simplistic thinking. And behind such simplifications there is usually propaganda. Evil people try to hide among other people. They try to deflect criticism by using this kind of simplification.