Some people praised the killing if the Israeli teens. The killers of the Arab teens did get support from extremist elements in Israel. Hamas denied involvement in the killing of the Israelis and the press in its attempts to pin it on Hamas made some vague claims that various people praised it. I think Hamas praised it when it was a kidnapping hoping it could be used as a prisoner exchange, but using google I was unable to find any evidence that their murder was praised by Hamas. The praises were all on the context of Israel releasing Palestinian prisoners as far as I can see.
To me the murder of the Israelis was a kidnapping gone bad, the massive Israeli response likely cause the kidnappers to panic. The murder of the arab kid was especially evil as they took him with the express intent to horribly torture him to death. It was incredibly sadistic. They took him to a forest, and doused him with gasoline and set him on fire. Utterly evil. The students were kidnapped initially with the hopes of exchanging them for Pali prisoners as is most of these kidnappings. But the overreaction by the Israeli authorities probably panicked the kidnappers.
