I disagree with your assertion that S think it's okay to do this to kosher products, and would treat halal differently.
It seems to me that a scared and hard-of-thinking manager made a decision because a load of people scared his staff. I don't think his/her decision is evidence of anti-Semitism on the part of Sainsbury's.
However, it clearly demonstrates the anti-Semitism behind some of the protests against what is happening in Gaza. I don't know what the answer is, because I rather suspect that people who smash up kosher food don't care that the state of Israel =/= Jewish people. And don't care.