Maybe they object to mass murder of civilians, children and the deliberate starvation of 2 million people.

It's not particularly complicated, what Israel is deliberately perpetrating is something that normal, uninvolved people cannot agree with, it horrifies and disgusts them and they will forever associate these actions with Israel.

Even with Israels deep political connections and influence committing ethnic cleansing and a genocide is not something that they will ever be able to whitewash away, no matter how they contort the situation.