Unless of course this is a true phobia that really ought to be dealt with, slowly, by a therapist, in which case going to this Church camp could be quite damaging for him.
I agree 100%. Although true phobias are often irrational, they are very real. And though most therapists favor exposure to the fear as a means of controlling it, the exposure is gradual. If you truly have a phobia and not simply nervousness at trying something new, then you would probably benefit from therapy. Some things to think about before you decline your priest:
1. What makes you think this might be a phobia? What has happened in the past when you were away from home/family?
2. Can you arrange for a friend to go with you? Someone you can trust with your situation? How about the priest? Can he help you while you are there?
Whether or not this is a real phobia, you won't want to let this control you. Fears have caused a lot of pain and heartache for people because they let the fear control them and missed out on so much in life. Take it from someone who's gone through it- fear controlled me for quite awhile, even to the point where I avoided situations. But, with therapy, I control the fear nowadays and not the other way around. There's help, bubba.