I'm pretty sure you can subsitute anti-war protesters with scum (in THIS article) and the article would read just as well
IMO the reasoning they did it is irrelevent. They vandalized a memorial created by the COMMUNITY for 9/11. I stress that it was created by the community because this was not a gov't action that created the memorial, it was a band of people that wanted to show their emotions for a very traumatic event. The memorial had NOTHING to do with the war.
I think the owner should press charges, and nail 'em.
The memorial was on private property, this goes beyond any free speech because the vandalized items were NOT owned by the vandalizers.
If the property owner decided to go ballistic and trash the memorial then yes it would be freedom of speech because it is on his property (still would be wrong IMO but thats another story), however the vandalizers did not own it and therefore it is a crime.
Apparently the police in that area either aren't so bright, or they support the vandalizers actions (or their all good buddies

)