We are required, in our love for the lost, to speak the truth. It doesn’t help Muslims for us to pretend that Islam is peace. If a Muslim wants to make up his own religion, okay, but he can’t call it Islam. That is an established religion with founder, scriptures, and history—and it is the opposite of peace and tolerance. You will do your Muslim friends a disservice if you avoid the truth so as not to offend.
"He that speaketh truth sheweth forth righteousness: but a false witness deceit."