Is the term Crusaders and insult?

It is only recently that the original crusaders have been understood to be foolish and wrong. At the time your school mascot was named, the word "crusader" referred to a valiant person with energy and purpose, someone who really cared about something enough to do something about it, someone like you, actually, as you are addressing this issue. Being Christian was not understood to have anything to do with it. Just the caring part. I would say, cut those people some slack, and direct your own crusading to a more worthy cause. There are other situations that can benefit a whole lot from your noble attention. You can make everybody happy instead of making them feel guilty and bad about things they never meant any harm about.