First of all, let’s not conflate criticism of Israel with anti-semitism. I am an ardent opponent of anti-semitism, and while criticism of Israel may well be used as a dog-whistle among anti-semites, that doesn’t mean that all criticism of Israel is inherently anti-semitic. Indeed, I am very happy to know that there are many Jewish people who oppose Israel’s genocide who I can stand with.

As for your question - I don’t believe any individual person’s claims of genocide, but rather consider the evidence. These are the facts as I know them:

1. Israeli politicians have gone on-record, several times, all the way back to David Ben-Gurion, about their intent to, at the very least, displace, the arab population in and around Israel. In more modern times, the rhetoric is far stronger and very dehumanising.
2. Israel has continually treated Arab Israelis as, at best, second class citizens, denying them citizenship and property rights, displacing them, causing them to flee in conflict and refusing them the right to return to their homes.
3. Israel built a wall around Gaza, tightly controlling the flow of people, food, water, medicine and other forms of aid into Gaza. The West bank, Gaza and East Jerusalem have been illegally occupied by Israel since 1971.
4. A series of conflicts have seen Israeli employing overwhelming and disproportionate military force against Arabs indiscriminately, bombing schools, hospitals, residences, and destroying vital infrastructure, as well as maiming, killing or imprisoning journalists, human rights monitors, aid workers, and so on.

I could go on, but honestly, that’s enough for me to call it like I see it. Israel’s grand ambitions extend at least as far as driving all Arabs out of the territory immediately surrounding Israel, from the banks of the River Jordan to the Mediterranean sea, and possibly further. They are willing to go to any lengths to achieve that goal, including war crimes, crimes against humanity, extrajudicial killings, mass murder, bombing civilians, destroying schools, hospitals, mosques, regardless of who is inside, they’re willing to illegally push people out of their homes, bulldoze Palestinian settlements, steal, kill, and lie about it the whole time they’re doing it.