"when only Israel is singled out"

For criticism of Israeli policy? That doesn't even make sense. 

"Arab Palestinians in the West Bank are not Israeli citizens"

Right. They live under a brutal, criminal military occupation, the longest in modern history, as they're slowly pushed out of their homes and their land is steadily gobbled up.

"Gaza is in a state of war with"

No, under the law, Gaza also remains very much occupied. It is the subject of collective punishment designed to undermine Hamas, which Israel knows cannot be manipulated like the demonstrably-corrupt Fatah.

"Israel has no obligation to"

It does, actually, as the UN and all human rights organizations have repeatedly reiterated.

"(Palestinian) Israelis have full rights under the law"

On paper alone.

"Why picking out Israel?"

Because it is engaged in the most blatant, longest-running injustice of our time, one which would be particularly simple to bring to an end.