There are four main schools within the Vajrayana, or Tibetan Buddhist, tradition. These schools (Nyingma, Kagyu, Sakya and Gelug) generally work together harmoniously, although each school takes a particular approach to the cultivation of wisdom and compassion.
As with any spiritual tradition, Tibetan Buddhism has a small fringe of cult-like groups. One of these groups, known as the New Kadampa Tradition, has engaged in an ongoing series of public conflicts with the Dalai Lama. It's highly likely that the protesters you encountered came from this group.
Cultists invariably reveal themselves through certain repetitive behaviors. They insist on a unique perspective - a kind of fundamentalist approach. They engage in argument and disagreement, solely to bolster their own belief system. And they disparage anyone who suggests an expansive view of life - a kind of paranoid view of the world. You'll find cultists everywhere, even here on Yahoo Answers, but genuine Buddhism has no place for cultists.
The Tibetan Buddhist tradition is a source of great wisdom and profound understanding of the human mind. Of course, this could be said of any authentic Buddhist tradition. The most important thing is to encounter a keen-eyed teacher in an authentic tradition.
Best wishes on your path!