When is criticism appropriate?
No one who supports Israel is obligated to agree with everything the Israeli government does. The only ones who have to defend Israeli actions are people employed by the government to do so. The reality is that we all have our own opinions and may disagree with one or another policy and, sometimes, an action is just difficult to explain.
Rather than feeling a need to defend Israeli actions, you should be able to put them in context. Remember, most people you encounter will know little or nothing about Israel, so they will make judgements based often on what they see or hear in the media. Regardless, of your personal view, you should be able to explain why a policy was adopted or the different arguments in Israel. For example, you make oppose settlements or believe they are essential to Israel’s security, but, in either case, when speaking to a general audience it is more important to explain the conflicting views than to simply pontificate your own.
Know your audience
This does not mean your personal opinion needs to be stifled. The question is how to express it in the most effective way. As any public speaking teacher will tell you, one of the first rules before speaking is to know your audience. If you are speaking among fellow supporters of Israel, criticism means something very different than if you express the same views to a neutral, hostile or ill-informed audience. Among those who share your love and knowledge of Israel, it is reasonable to express concerns because the audience knows that you are interested in seeing Israel be a better place and has similar information of the context of the policies you are criticizing. If, however, you express the same views in an audience that does not have the same concern or knowledge about Israel, all they will hear is the criticism and take that as indicative of Israeli policy.
For example, if you criticize the inequalities that exist between Israeli Jews and Arabs, an informed audience will know that under Israeli law both populations are treated equally, but, like in America, minorities continue to face some discrimination in practice. The same discussion in a more general audience, however, will come across as showing Israel to be a discriminatory society.
Do you want to make a difference or just get publicity?
If your goal is just to get notoriety then be the Jew who regularly attacks Israel. In the news business they say that is like a story of a person biting a dog, which is far more interesting than a story of a dog biting a person. Many individuals now tour campuses based on the fame they achieved by being anti-Israel Jews. If, however, you are interested in having some chance of influencing policy, then you should express your opinion in forums where the people who actually have the power to change that policy will listen to you because you have credibility.
Some people argue that it is okay to publicly criticize Israel just because Jews in Israel censure their government. America is not Israel; Israelis have a common narrative and shared experiences. Americans, even American Jews, do not have the same level of knowledge or experience with regard to Israel, so criticism is interpreted differently. Criticism is also not justified by Israeli encouragement as they do not understand the American context and they typically only bless critics who agree with them (leftist Israelis are happy to encourage American Jews to speak out against rightist governments but are furious with criticism of leftist governments and vice versa).