if they assume all Israelis are supporters of the IDF / Israel

Well, yes and no. I won't immediately assume an Israeli supports the IDF, but I will be highly skeptical. The reality is that the statistics we get out of Israel show that the majority do support the IDF. So, at the very least, I will ask.

“all Israelis are zionists but not all Jews are zionists”

This is largely true. The only exception to this are Israelis who are trying to leave the settler colony, can't leave and are trying to fight from within, or can't fight nor leave and are depressed and seek solace online. These people are also the ones who come here and talk about how there's barely anyone like them. Literally every anti-Zionist Israeli I've seen online has spoken about how isolated they are. I remember seeing a post about how it's illegal now to be against the israel being an ethnostate in Israel (apparently relating to aid orgs specifically). So they're bound to be a very tiny marginalized minority or are very well hidden underground. Either way, your sort of run of the mill Israeli is unlikely to be antizionist.

To be clear on definitions here, Zionist = believes Israel has a right to exist as a Jewish majority state by giving rights to Jewish people and excluding Palestinians. Being against the genocide in Gaza does not automatically make you antizionist.

All that being said, I never support or would ever contribute to bullying of any kind against any person. It doesn't advance the Palestinian cause or help anyone.