Does Israel have the right to defend itself? Absolutely - just as every other nation in the world does. And, anyone who says otherwise - is likely in the category of wanting to see Israel destroyed - including several who already posted nonsense here.
Does Israel have the right to a pre-emptive strike? Again, yes.
As for the ridiculous assertion that Israel was somehow wrong to pre-emptively strike in the past - let's look at history:
1967 - this was the first pre-emptive strike (after being attacked by 5 Arab countries in 1948, 3 in 1956, and repeatedly before, between and after these dates). In 1967, Egypt and Syria made it clear they were about to attack - Israel simply chose the time and was able to save its own citizens by fighting on its terms.
In 1973, the Arabs attacked on Yom Kippur - knowing that the majority of Israelis would be in synagogues praying? All of you people who complained about Israel striking pre-emptively - have you no complaint about the Arab actions there?
In terms of the Palestinians - it is all very clear to anyone willing to really look at the situation. As Israel's UN Ambassador said recently - "when you sleep with a missile, sometimes you don't wake up." That does for the Lebanese as well as the Palestinians.
To see more about terror attacks on Israel - and the results of the Lebanon War - the one started by Hizbullah when they crossed INTO sovereign Israeli territory and murdered and kidnapped Israeli soldiers - see www.paulasays.com. There's a link there to several PowerPoint presentations created by someone living in Haifa who witnessed dozens of katyusha rocket attacks.
The old saying is simple, but true - If the Arabs stop their aggression and terrorism, we'll have peace in the Middle East. If the Israelis stop...there'll be no Israel.