They get mad the same reason as non-christians get mad. We are all plagued by an over inflated ego of always wanting to win and always wanting to be right... when you test a Christian by proving him/her wrong... YOU are actually doing christ's work, you are testing their patience to help them build MORE patience, you are shaking their faith which will reveal IF they are truly faithful or they are just doing a show.... . Obviously as with all people, Christians will fail too, and with God's help they will pick themselves up and try again.... I mean... if the wisest man on earth, Solomon could be tricked and lured into a trap, what more the rest of us... we will all fail at least once, but failure means persevering for the next test.