I wouldn't say it offends me. I don't like it. There are two main reasons:
1. It's factually wrong. Arab people have huge issues and face a lot of racism in Israel, but also enjoy equality under the law and reach positions of power. Israel is more similar to other countries with minorities facing problems than to South Africa. The situation in the West Bank isn't appartheid- it's a military occupation,. This is of course a terrible situation we need to end, but both sides need to compromise for this to happen. Just doesn't bear any resemblance to appartheid. Of course, if Israel annexes territories without giving the Palestinians there a right to vote, that would be a move towards appartheid and I will readily admit it.
2. The constant use of the word appartheid to describe the situation joins other flaws in the arguments of people on the left- the overuse of words like fascism, genocide, colonialism etc. This cheapens the very grave meaning of the word and makes it a partisan issue.
I should point out that, as Desmond Tutu said, Israel itself is not an apartheid state. But the West Bank and President Abbas having a separate government, with hundreds of divided up, small pieces of land, is exactly like the Bantustan system with an elected government. Apartheid implies segregation and entire groups of people unable to vote. But in the sense of one group giving the other group separate elections while maintaining power and security over them, especially by using cartographic gerrymandering, the West Bank is currently very similar to Bantustans in South Africa.