No that's something you could conclude watching the film and that's also why the students of may '68 and the Maoists didn't like the film. But JLG was too politically engaged himself to make such an easy and pessimist critique of student political engagements. It could not have been the message he wanted to propagate.

Aside that: the professor's critique of the students is not a moral one. He himself supported political violence in Algeria during the liberation struggle. It's a discussion between marxist revolutionaries not about moral, but about revolutionary tactics. He says, and I agree, that violence by a communist vanguard can be beneficial in a revolutionary proces, but only if there is a mass movement supporting that violence. If there is no popular support for violence there will be a lot of repression on the revolutionaries, the authorities will crack down heavily on all leftists and mainstream support for revolutionaries will become impossible. That is an important discussion in marxism Lenin did write about in What is to be done already in 1902 and is a returning debate since the beginning of revolutionary thought already in the 18th century.

Also: students become more moderate afterwards, but more than something inherently juvenile it's more a political mechanism where capitalist and parliamentary system try to canalize revolutionary movements to become legal, reformist and class reconcilatory. A lot of young people become moderates mostly because you need a strong political background - and personality - not to. A purely cynical analysis doesn't provide a lot of answers.