Legitimacy is a value-loaded term that cannot be about peoples or states who either exist or not. Legitimacy is about the actions of peoples and states; not about their existence.
Are Muslims legitimate? Are Jews legitimate? Are Baha’is legitimate? Are Martians legitimate? Is Israel legitimate? Is Canada legitimate? Is Egypt legitimate? Those are meaningless, misleading questions that – at best ignorantly and at worst deliberately – miss the point. The more appropriate questions that require answers to guide human judgment are:
Is the need of people (Jews and otherwise) for security and safety legitimate?
Is the need of people (Swiss and otherwise) for a place they can call home legitimate?
Is discriminating among peoples on the basis of race, ethnicity, or religion legitimate?
Is dispossession of people’s property legitimate?
Is colonization legitimate?
Is destruction of schools, medical facilities, and places of worship legitimate?
Is uprooting trees and destroying people’s livelihoods legitimate?
Is imposing a specific “diet” on one and a half million people legitimate?
Is collective punishment legitimate?
Is ethnic cleansing legitimate?
Is apartheid system of government legitimate?
Is violating international law legitimate?
Is deliberate killing of women and children legitimate?
Is extrajudicial murder legitimate?
Is the abduction of humans by Martians legitimate?
And a few more questions that have to do with policies and actions; not with entities.
Once those questions are answered, reasonably intelligent people can then move to discussing the legitimacy of the ideology that drives Israeli policies and actions. Israel exists, and denying that fact is plain silly; just as denying the existence of Liechtenstein would be. However, it is Israeli policies and actions that are rightfully being questioned for their legitimacy.
Hope is the stuff from which life is made!