This is just trying to dismiss European and in particular here British responsibility for the situation. There is so much fighting all over the world that can be directly traced back to how colonial powers divided up the world. Various civil wars and genocides in Africa because completely different ethnic groups were shoved together into one country. We currently Venezuela and Guyana. Pakistan and India for decades (which is possibly closest to Israel and Palestine). Israel and Palestine. I'm sure there are more. I think it's pathetic to say, "well this happened decades ago, you should have sorted your **** out by now, it's not our fault anymore". As for it happening throughout history, yes it has, but that doesn't make it right or excuse it. In fact often it just led to more wars and oppression in those places. Slavery has also happened throughout history. We don't shrug our shoulders and say tough it's part of life.
Does Israel have a right to exist? As Ragey said, it's not a simple question. Does the Basque region have the right to exist as a separate state? How about Christians, Buddhists and other religious groups, do they have the right to their own state? Now you'll probably say they already do, which is and isn't true. Some countries use religion as the basis of their state, but many don't. The state and the religion are usually separate and most are secular states. Israel (despite it's propaganda isn't a secular state) many of it's laws actively favour Jewish people. I am personally opposed to any state that is based on one religion. For me anyway, organised religion itself is just politics with a religious tint. Religion should be personal to the individual and religious organisations should be there to guide people, not enforce.
As for Jewish people as an ethnic group, well this is just as complex. In theory I guess the majority of Jewish people are descended from those in Israel if the concept of being Jewish through the mother's side is consistently accurate. However, as Jewish people will have married non-Jewish people throughout history this will have become more and more confusing. But again does every individual ethnic group have the right to a state? At what point do you class someone as ethnically Jewish? The same for other ethnic groups.
Then even of you come up with an agreed definition if that group doesn't have land then how do you decide where they go? Who should be forced to give up their land to make space? That's exactly what happened in Palestine and look at the conflict and atrocities it has caused. I am definitely anti-Zionist when it comes to creating an Israeli state by forcibly removing people from their homes and land. (which has happened). I am anti-Zionist if it means creating a religious state where not everyone is equal (which has also happened). Tbh I would be anti-Zionist in general because I believe that humans need to work together and we need to move on from the concept of a national state. For me all nationalism continues to do is separate and divide us as a species. We're at a point where we need to address global issues that transcend national identities and the reality is we can only do this as a species, not individual states. We can also do this in a way that respects people's heritages and traditions.
For me though that does not make me anti-Semitic.