I have no doubt that most Western critics of Israel are genuinely critics of Israel and not anti-Semitic (as they are not the same of course), but I also have no doubt that those who are sending the rockets really do hate the Jews, and they too have their small (but apparently growing) band of anti-Semitic cheerleaders in the West. I just urge my friends critical of Israel to be mindful of the way in which they, by appearing to portray Hamas as relatively innocent victims, might be "useful idiots" for those who really are deeply anti-Semitic and would not think twice about driving the Jews into the sea.
Also, appearances matter too. Too often, that sympathy for innocent Palestinian victims comes across as being too soft on Hamas and those who really would exterminate the Jews. I just think the critics have to be very careful not to mention more frequently note that it's not just states that initiate violence against innocents and publicly criticize those who do so.