What makes you a legitimate target?

In the eyes of the righteous, it would appear to be free speech.
This article in today's Guardian features Laurie Pycroft, the founder of PRO-Test and one of the speakers at today's march in Cambridge proclaiming support for animal testing. He expects that putting his right to free speech to use will cause him problems:

"The worry is I am going to be targeted for property damage or worse, but it's something I have to live with if I am going to get my point across," he says. "It is sad that in this country where we are meant to have free speech, I can't have free speech without the police coming round and talking to us."

It is scandalous that the police continue to focus the powers of the government's anti-terrorism legislation onto such trivial incidents as hecklers at the Labour Party Conference or a lone female reading out the names of dead soldiers near parliament. Meanwhile, the Taliban-esque core members at the heart of the animal rights movement remain unfettered in their ability to harass, antagonize and ultimately terrorise anyone who they consider as a "legitimate target". The UK is considered as being "an Afghanistan of animal rights extremism" by the US. While this might cause some unease given the tendency of the US to over-exaggerate, it nonetheless emphasises just how easy a ride that these extremists have been given. With the current climate meaning that police resources are focused on Islamic extremism, it could be the case that a different flavour of extremist, every bit as fanatical and dangerous as the religious type, makes an unwanted impact on our liberties.