I'm not familiar with that organization so I can't comment on that. I assume they're not unless proven otherwise.

And what indiscriminate slaughter?

Attacking a music festival and murdering 260 unarmed civilians for example.

Even if I grant you that Israel is located on occupied land, that still doesn't make every Israeli an occupier because many of them were born there and had no say on the matter, and even if you count them as occupiers too I still don't think the optimal solution is to murder them.