It is not that the left hates the idea community, quite the contrary they want to impose their rigid ideas of community on us and political correctness is only a foretaste, rather it is that they hate any conception of community which competes with their own. So the decency of "Leave It to Beaver" is anathema to the left not because it was inherently undesirable that people help each other in time of need as you describe but the opposite, because it was attractive, because it was decent.
In fact I think the left has taken the idea community and exploited it which explains much of the appeal of leftism. The best historical reference I can make is to the EST movement of the 1970s which sought to strip away the individuality of the victim and remold him into an "EST-hole." This is really the meaning of "drink the Kool-Aid" in which the individual abandons his responsibility to himself to think for himself and submits himself, his conscious being, his conscience, his power to reason, to the "community."
This is what I think Hillary Clinton was driving at when she talked about yearning for an "ecstatic experience" in her graduation address at Wellesley. She was speaking of the emotional and psychic release obtained by such a surrender of the will, by such an immersion. I think this is a key part of why the left is so emotional about their candidates and so irrational in their thinking. When a subject is in this state it is easy for him to despise a decent culture which they caricature as "Leave It to Beaver."
