They obviously suffer from impaired cognition. Whether it results from brainwashing or a congenital cognitive deficit is irrelevant. The moral justification for violence against property is even clearer. If violence against property is wrong, then the American colonists shouldn't have thrown all that tea in the harbor and Jesus shouldn't have kicked over the tables of the money changers. However, just because violence is morally justified in some situations does not mean it is required, or that it is necessarily the wisest thing to do.
All actions have consequences.
Consequences, not the musings of moralists, are the most important aspect of any action. Pay particular attention to who actually benefits. It isn't always immediately obvious. Keep in mind at all times that the property destroyed by the ALF and ELF is heavily insured. Insurance fraud by arson is exceedingly common.