You need to differentiate. There is a lot of criticism against Israel as a state which is anti-semitism in my opinion because people plainly suggest different rules just for jews.
Then there is criticism against the settlements which in my opinion steals land that doesn't belong to those that want to settle there. The criticism is valid. There is a cultural component here though as many settlers were formerly expelled from Arab lands. That influences in what they see as just.
In reality this criticism gets horribly mixed and objective debate is difficult. Many in Israel are sick of the conflict and wary about criticism because they always have to check the motivation behind it.
Those that propose to defend the side of Palestinians often aren't the best in my opinion, even if they have been fully socialized in western nations they still demand the destruction of Israel. That is stupid beyond measure and certainly not conductive to solve the conflict. Some probably have a worse effect than terrorist groups.