(pt. 2)
it is unclear what the word "communist" means anymore. It seems to evoke different things depending on your education, your country of origin, your attitude towards tradition and/or conventional authorities, etc.
most of the youth in the streets in Montréal recently, who have upheld the Palestinian cause in a way that occasionally involves putting their bodies on the line, do not call themselves communists. More of them probably call themselves anarchists than communists (although that is still not likely very many people)
the message of "Libérez la Palestine!" is good, and the facts are fine. But most people already know these things - and those who reject them are that much more likely to reject them in this case because these are now the words of "communists"