I volunteered for the first time this year with Oxfam at Glastonbury and quite honestly couldn't disagree more. You are provided a "safer" place to camp, facilities, food and a festival ticket all in exchange for 24 hours work. The ticket cost alone makes that worth at least £10 an hour, which is pretty insane considering you are a volunteer!
The Oxfam management were pretty open with the fact that people make mistakes and over-estimate their abilities to recover from drink/drugs/general exhaustion and promoted being honest to them so they could move your shifts, help you out or whatever else is deemed appropriate.
Personally I would have preferred a ticket however volunteering is still a clear amount better than not going at all!
What did you actually experience? It sounds like you just had a disagreement with your supervisor and that has tarnished all volunteering prospects for you in the future?