1) The attack came before Israel did anything. Your logic requires a time machine.You mean like the five Arab armies as soon as Israel was declared as a state?So, no concessions to any parties that want to invade land and steal resources rather than negotiate peacefully for mutual benefit.
I mean like Zionists murdering thousands and driving out hundreds of thousands of people so they could create an ethno-state with the intention that only Jews would be allowed entry and only Jews would be granted full rights of citizenship.
2) The vast majority of those who left did so at Arab behest. And then weren't allowed to return when they refused to accept the Israeli government. Why should Israel allow enemy agents into the country??