I used to feel very much the same way about no sympathy for violent groups, but then I realise that some people feel (rightly or wrongly, is up for you to decide) that the democratic process does not or even cannot accomodate the kind of change they want to see - not because they see democracy as unable to acheive emancipatory goals, but because they see democracy as having been brought under the rule of capital and media rather than by an informed and active demos.

As my favourite social critic Marcuse wrote, when the democratic process is blocked, apparently undemocratic means may be required to unblock it.

Where does it say "violent" protests?

This outlook is a very privileged one. Outside your community, violence may not be an option.