Hard to say. I know among the people I know personally quite a few of them. I myself above said there's plenty of blame to go around on each side for the violence in that region.
Some of the people that have commented on Israel might have some reasonable comments about Palestine and Hamas' responsibilities as well. Often we are only given a brief snippet of what people say on the news so as far as politicians it would require a lot of research.
I'd bet that some of the people criticizing Israel are doing so due to antisemitism but there are likely many people that aren't. It shouldn't be a surprise that lots of people are generally anti-war and anti-human suffering in general.
My issue is that people are so quick to claim antisemitism at the slightest criticism that its more reasonable to assume that the people who do so are hysterically pro-Israel than to assume the person that was being critical is an antisemite.
Another thing to consider is that even if a person decides that Israel is entirely at fault, you and I might disagree with them, but that opinion could easily have nothing to do with Judaism.
The thing is, people on the left emphasize more with being expropriated for no good reasons, having strikes broken by threatening families and generally being treated as 3rd class citizens, than being threatened with missiles. At least I do. I understand that both sides are shit, but I will still boycott Israel products, as i boycott China's.