Because if yes, Zionism is an ideology in favour of ethnic cleansing, which is an uncomfortable spot to sit...
I think it's reasonable to oppose those. Though I'm skeptical the settlements make any real difference in the situation. Removing them from the Gaza Strip didn't seem to make any difference, why would removing them from the West Bank help?
Basically, to stop this kind of conflict takes dialogue. Lots and lots of dialogue, with people who are serious about it. And not stopping the expansion of the West Bank settlements as per the Oslo Accords signaled that the Israeli government was not serious about its commitments.
(Hi, I'm Irish, I have a small idea whereof I speak, though not much.)
Illegally putting "facts on the ground" through settlements is a big deal to the Palestinians and it's a big deal to everyone else. It needs to stop.
(aside: There's a long distance between "please stop allowing or encouraging your government to treat other human beings in this terrible, terrible manner. Please think about the crimes done to them by your parents and grandparents - and by you. Please consider how you can encourage peace," and "we hate you." Or there should be, anyway; there are some very invested people.)
When they make settlements it disturbs the peace process; when they unilaterally remove settlements, it also undermines the peace process. When they bomb or occupy a neighboring country it's an overreaction, but when that neighboring country is firing rockets into Israeli neighborhoods it isn't their responsibility. When a terrorist hate group takes control of Gaza and breaks away from the Palestinian Authority, they aren't disturbing the peace process, but when Israel and Egypt jointly declare a blockade on Gaza and Israel captures a "flotilla" trying to run the blockade, Israel are the oppressors--even though the supplies carried on the flotilla were merely inspected and passed through to Gaza anyway.
It's generous, and likely accurate, to say that those who hate Israel aren't thinking critically. Most people who take up intellectual fashions aren't thinking critically--that's why they take up intellectual fashions in the first place. But the more passionate ones are likely antisemitic. There are fair criticisms to be made, but there are also plenty of double standards at play as well.
That tar-brush you're waving around is very, very wide.
Perhaps McGuinness is reformed (you did say former member of the IRA army council). Does he continue to call for the destruction of Great Britain? If not, you can negotiate with that. Israel has long negotiated with Palestinian factions that endorse a two-state solution, such as Fatah. Mandela accomplished the destruction of apartheid, and it was only by De Klerk's agreement to the end of apartheid that he and Mandela could deal with each other. With Hamas, only the destruction of Israel will suffice. What exactly is there to deal with?
This is the power of dialogue. You talk, you talk, you keep talking. You deal with the less extreme popular factions (analogy: https://en.wikipedia.org/wiki/SDLP), but the key word in that sentence is popular: an agreement with an organization with no backing in the community is an agreement with no-one. You do NOT commit to something and then completely disregard it, because then your word becomes worthless, and no-one believes anything you say ever again.
I do not know the solution. No-one does. But attempting to push the Palestinians into the sea is not it.
We can agree that Israel has made a lot of mistakes. That doesn't legitimate groups like Hamas and that doesn't provide any basis for dialogue with Hamas, either. Meanwhile, the anger and hatred towards Israel would be there with or without the mistakes. It was there before the mistakes and it will be there long afterwards.