1) No it's not. By definition if I think one thing is right (i.e. Jesus is God's Son) and a Muslim thinks another thing is right (i.e God has no son) those two claims cannot be both true.
2) What is definitely wrong, is trying to stop people from teaching what they claim is a religious truth. The first amendment is very clear on this. The right to believe and teach as you believe, even if it's in conflict with another is a fundamental freedom of conscience.
For years, I could sit at a table with atheists, Jews, Muslims and Wiccans and have wonderful discussions and even arguments about which of us was right.
But the one thing we never did was tell the other person they did not have the right to:
1) Explore whatever religion they wanted to.
2) Teach whatever religion they wanted to (including that others were wrong)
3) Try to shut the others up as long as they were being more or less civil.
Honestly, it was a stretch between the Muslim and the Jewish guy one of them quit hanging out.
I'm actually offended more by the idea of trying to stop people from teaching something they hold near and dear to their heart than I am by people teaching something opposite of what I believe.