It's used specifically for the purpose of shutting people up and intimidating them so they will not speak up for equal rights, and it's definitely true that many people have been harmed by the cynical use of this tactic by supporters of the government of Israel. However, I think it's beginning to lose its punch because of its overuse, like for instance, by the people here in this thread who have used it to try to silence me. Personally, I don't see any need to defend myself against this accusation, because intelligent people who have read my posting history can see right through it.