I doubt any sane person would deny that the USA and the UK are democratic countries. Yet both states reserve the right to refuse entry to individuals who they deem a risk to national security. Last year Geert Wilders, a dutch MP (imagine that!) and European Citizen was prevented from screening his film in the UK. Labour even drew up a blacklist of foreigners liable to incite violence and sedition. Chomsky has a track record of supporting genocidal and/or tyrannical regimes (Cambodia under Pol Pot, Communist North Vietnam, Cuba) and has publicly endorsed Hezbollah, a theocratic group that has vowed to wage total war against Israel and anyone in Lebanon that might oppose it. Why should Israel provide a forum to enemies of democracy, from the left or the right? As for internal criticism, laws safeguarding free speech are still in effect, if even if Israeli politics suck at the moment.
U.S.-led coalition conducts 14 airstrikes against ISIS targets in Iraq, Syria (Reuters)
from the article: Noam Chomsky denied entry into Israel and West Bank