That's certainly possible.Even if some (or even many) of the Guardsmen had real experience in,say,Vietnam I would think that that wouldn't qualify them to handle a riot.My feeling is that handling riots requires a very special kind of training and back then the National Guard was known pretty much to be a joke.
I am not saying that busting heads was the answer but if they put many of them in jail and had them do a year or so consistantly the problem would have been smaller. If I recall correctly hippies didn'r have a lot of nads at least in Boston.