As you've read, horses were used in yesterday's terror raid. Some say they were actually booby-trapped as if to be used in place of suicide bombers.
I initiated a campaign back in 2003, after friends of mine narrowly escaped injury and death when a donkey packed with explosives was blown up at the Gush Etzion checkpoint. I targeted PETA, wrote to the head office and 15 other branches complaining about the misuse of animals this way and achieved the sending of a letter of protest by them.
Every little bit counts.
Why don't you write to PETA and simply ask them to condemn the terrorists who not only have no regard for Jewish lives but for animals, too.