The Well Intentioned, But Ignorant, Dogmatist

This past week my parents, my brother and I helped out with my sister's youth group. Anna's youth pastor, Richard, dedicated a whole week to "Bible Boot Camp" in an effort to get this group of kids excited about learning the BIble. The first day was all about benefits of knowing what's in the Bible. The second day was on the Old Testament. The third day was on the New Testament. And the last day was on how to do a Bible Study on your own. So cool.
One of the speakers at Bible Boot Camp was a man who I will call Bob. The reason I bring up Bob is because in meeting Bob, I encountered what I will hitherto refer to as "the well intentioned, but ignorant, dogmatist." Allow me to illustrate. 
Bob taught the youth group kids that in order to go to heaven, you must believe in the Triune nature of God, the inerrancy of scripture, the ecclesial calling of the church and the redemptive power of Jesus' death and resurrection. While I think we can all agree, as Christians, that those things are important, I doubt that misunderstanding something as complicated as the Triune nature of God will keep people out of heaven. If this was the only thing Bob said that bothered me, I wouldn't have bothered mentioning him, but wait, there's more.
Bob also mentioned, when talking about other religions, that Muslim's worship a rock, that the Book of Mormon is nothing more than a plagiarized King James Bible, that no one in history ever claimed to be God besides Jesus, and that Satan is actively working through these other religions to lead Christians astray.
It gets better. Bob also said that you have to be wary of Darwinists because they'll lead you to believe that science proves the earth is billions of years old. Scientists just lie all the time anyway. There is no proof to believe the Big Bang theory, it's a fantasy. Stellar evolution has never been observed, we've never observed the formation of larger elements from hydrogen, and there is no archaelogical proof that the earth is older than 10,000 years. Perhaps my favorite comment that he made all week is that Stephen Hawking is just a nut and you don't have to listen to a word of his theory because he only does it in order to disprove God.
Needless to say, Bob is more than a little misinformed. I don't know where he got all his information, but he's wrong about 90% of the time.
His goal, of course, was a good one: to give confidence to these young kids that their religion is trustworthy and that there are answers out there no matter what opposition they encounter. However, what do we do, as educated young adults, with Christians like this? How do we approach people in the church who have wonderful intentions and who never waver in their faith, but who give inaccurate information and reasons for why we can be certain of our faith?
I admit I don't have an answer to my questions, which is why I'm writing to you. We all know that we will encounter, not just ignorant people who DISAGREE with our worldview, but ignorant people who AGREE with our worldview. How do you avoid "in-fighting" and how do you gently approach people who are just wrongly informed? I'm truly baffled by this man and would appreciate your help.

Lydia