First: Neo-nazism is a right-wing ideology. Full stop. There are no nazis on the left, because if they were subscribing to nazi ideology then they’re on the right.

Second: Generally speaking, you aren’t seeing anti-semitism on the left, you’re seeing opposition to Israeli policies that cause direct harm to Palestinian people, e.g. refusal to engage in a serious attempts at a two state solution, indiscriminate bombing that’s killed over 20,000 people so far. of which roughly 75% are non-militant women and children, and so on. You’re interpreting opposition to Israel, a country–a country that is also an apartheid ethnostate–as opposition to an religious-ethnic group. That is as dumb as saying that opposition to Iran politics, policies, and action (actions like, say, arming Hezbollah and Hamas) is the same as being anti-muslim.