I can understand your annoyance, and it doesn't sound like he handled the situation very well. However, in practical terms, there is just no way that every canvasser is going to be up to date on every aspect of party policy. It's just too much information for those who are not full-time politicians. Usually when I get asked something that I'm not sure about, I'll just let them know straight off, and (if possible) get the candidate onto the doorstep quickly.
I would suggest that you don't base your vote on what happened on your doorstep either way.