Under other circumstances, it could be. But if the information we have so far is correct, making an issue of this scuffle could result in enforcement of Israel's law against preaching the gospel to Jews. Visas could be pulled and then the mission would be over. A ripple effect could adversely affect other missions in that country.
You're right -- Christians certainly have the right to defend themselves. But they also have the right not to.
There is no such law. It's against the law to proselytize minors, or to pay for conversion, but thats it.
If their intent was to cause a confrontation, likely as this neighborhood isn't fertile ground for proselytization, I suppose that could become a visa issue. Obviously the choice of what to do is theirs.