Very very few vegans support bombs and arson because as you pointed out it risks harming people. Many do support non violent actions such as rescuing animals or property damage. It's very much a case of one man's freedom fighter another man's terrorist.

Plenty of revolutions have involved violence, apartheid and anti slavery for example, so I don't think the simple fact that a campaign uses violence makes it terrorism. Ultimately the ALF are trying to stop violence being inflicted on innocent and defenceless animals for no reason.