because there's a difference between weapons used to defend, and weapons used to offend. Israel recognizes it's neighbors, do Israel's neighbord recognize Israel? As in, a right to even exist as a country? The decoy here is Arab nations pretend they need weapons to "defend" an Israeli invasion, when really the motive for Arab nations have never changed since the day after Israel declared a state in 1948. THAT, is the difference. Your question makes about as much sense as what is the difference between you owning a gun to defend yourself, and a crazy person owning a gun who doesn't like you because you don't believe in his religion....
Saudi policeman killed in Mecca after Islamic State raid (Reuters)
from the article: MESS Report / Nobody wants war, but Israel-Lebanon border is heating up