Legally speaking, "retaliation" can only occur if your employer treats you less favorably after you report discriminatory practices.

The company is allowed to treat you less favorably or even fire you for any other (non-protected) reason, including your general opinions. In this case, protesting a deal with Israel is an opinion not a protected action, so there's really no question of retaliation.

If I disagree (whether publicly or privately) with my company's product strategy or who they choose to do business with, they are absolutely allowed to fire me.