Is there any good reason why a Jew should not waste his time engaging with anti semites either in real life or online? Thank you.
Isn’t you question self answering? Most of us would say that wasting one’s time is a good reason not to do something! Nevertheless, it isn’t just wasting one’s time, fighting and engaging anti semitism can actually make it worse.
The Midrash (brought in Rashi Bereishis 33-4) says from R’ Shimon bar Yochai ‘it is a well known law that Eisav hates Yackov” – anti semitism. It is an emotional hate, and it will come out at times as various excuses, and at times without any excuses. Fighting the haters, is not going to change their minds, to the contrary, when a person gets into a fight, they fight harder for their feelings, and it makes the situation even worse. It will cause worse hatred. Chazal tell us when dealing with the gentiles we should look to parshas Vayishlach, of how Yackov dealt with Esau. He tried placating him and lowered himself in front of him (not changing himself to be like him). By showing Esau that he respects him and he is humbling himself before him, that helped temporarily quell the antisemitism. Therefore fighting the gentiles, can actually make things worse. Yackov did not approach Esau with a sword drawn to fight him, rather the exact opposite. This that he prepared for battle was only as a last resort, if left with no choice, he wasn’t going to let himself get killed.
Having said this, it is important to stress that our comments here are only in general, and any specific instance has to be evaluated on a case by case basis, and should be discussed with gedolei hador.