Generally, I do not approve of this sort of thing. I find it rather counterproductive to the cause, and not effective in achieving goals that I think are important: the expansion of the average person's consciousness to include caring about animals, and the saving of animal lives. First, let me say that I do not disapprove of this type of action only because it is illegal. Animal liberation by way of breaking into labs and rescuing animals that are being experimented on is also illegal, but at least it fulfills one of the two above-mentioned goals, the saving of animal lives. I mostly have a neutral view of organizations such as the ALF, because I believe that sometimes people do feel powerless when faced with all the animal abuse going on around them, and believe that legal ways of saving these animals' lives are either non-existent or too complicated. I understand this.
However, liberating animals and spray-painting "meat is murder" on a restaurant window are two different things. The latter, although expressing a true and important sentiment, will do very little to raise awareness among the people who see it, most of whom will simply dismiss it as extremist vandalism. This, in turn, will make it harder to get these people to discuss animal suffering in the future. Thus, the effect on the opinions of customers and restaurant staff would be minimal, and the perpetrators will most likely be seen in a negative light. Apart from this, no animals will be saved by this action. All in all, it's an act born out of frustration, but there are better ways to get the point across. Instead of spray painting slogans, why not pass out pamphlets to people outside a restaurant, explaining why it's best to avoid eating meat? Why not pressure your politician to pass new laws that protect animals? Why not pressure your teacher (or your children's teacher) to set aside some time to talk to kids about animal rights and how to treat animals well? If direct liberation is your thing, why not get in touch with the Animal Liberation Front, and see how you can help them? Right there, off the top of my head, you have several things which would be much more productive than the above-mentioned vandalism.
