well the "unknown" member's behaviour sounds despicable to me.
From my (limited) dealings with James and observing his behaviour on the forums, I would concur with the general opinion that he is a very good mechanic and is (or was - but hopefully will remain) very helpful to others.
However, two points come to mind:
1) if you ask someone for help, you should judge them on their ability to do so ... not on their appearance, whether that be on their age, how they dress, or whatever. If you ask them to fix your car and they can't do the job, fair enough. But they should at least prove this to be the case - after all, if the person requesting help is that good then they should do the job themselves. It's standard practice in engineering fields that if you travel to a job and upon arrival you are not allowed to perform the job, then a charge is made for the abortive visit. It's only fair as the engineer has incurred expenses (fuel, etc) to get to site in the first place.
It's much the same as intelligence level - this is actually defined as POTENTIAL for learning. So you could have a person of a given intelligence level who works hard and knows a certain amount, then another person who is more intelligent - but is lazy and doesn't use that potential - they could actually know less than the less intelligent person!!
Likewise with age - just because someone is older doesn't necessarily mean that they are more experience and/or skilled than someone who is younger!
2) There are bad apples everywhere. Whether through internet or real life ... good ol' fleabay is a good example - at the end of the day some people have no standards or scruples and are only interested in themselves, don't let them cloud your judgement. Personally I wouldn't go out of my way to help that particular person again, but why tar everyone with the same brush? Benefit of the doubt and all that, after all I'd say a lot of the good community spirit on here is built through trust. People putting themselves out to help others that are effectively strangers ... if no one takes that initial risk then a lot of problems wouldn't get solved !!!
hopefully I'm not rambling too much - don't let the bast*rds get you down James