Is Evangelicalism a Mental Disease?

At a biblical studies conference last week I was having fun asking the politically incorrect question of the people I met as to whether or not they were a Christian.  To me, one's religious committments are bound to have a big affect on your scholarship (no matter what you say about "objectivity") and so I'm always keen to know, and at least I do it in person rather than public.  Well one very civilised chap I spoke to answered my question with a scowl and the statement "well, i'm not an evangelical" which was interesting, because I do self identify as such, but the way he said it I wasn't sure we would use the word in the same way.

But then reading about street preachers on Stuart's blog it occurred to me that for many evangelical is code for intolerance, bigotry, irrationality, right wing politics, emotional instability and public outbursts of hatred.  And this is the problem, I know lots and lots of evanglicals and they are by and large open minded, compassionate, polite, intelligent and a little shy.  How is it that such a huge majority has its reputation determined by a tiny excentric minority?

So really there are two meanings for this one word, and I wonder if like "fundamentalist" what was originally coined as a positive self descriptor will soon become an irreparably pejorative slur.  What do you think, is it a word you use of yourself?  To stand in the tradition of such conversionist and social activist examplars as Wesley and Wilberforce, for example, is no small thing, but then neither is being lumped in with every illiterate street preacher or free marketeering hawkish US politician.  Has the term reached the limit of it's usefulness?  Has it's broadness ceased to be useful for unity and become a liability to misunderstanding?

Let me know what you think.