First, the IDF is no longer in Lebanon.
Secondly, you probably know about the abducation of the 3 soldiers by Hizbullah terrorist, supported by the UN peacekeeping force from India.
The Israelis see UN troops cooperating with the terrorists and therefore sees them as ENEMY.
Officialy, they are not considered ENEMY, but a neutral force. But unofficialy, Israeli are mad at the UN for its anti-Israeli bias and its protection and support to Hizbullah terrorists.