I wouldn't make a voting decision purely on that, but when I was active in politics it was drummed into us that when canvassing you always shut garden gates, respected signs saying things like "don't knock, baby asleep" and generally showed your best face to everyone. Because in the words of Mr Darcy, "[a] good opinion once lost is lost forever".
Voters are less likely to choose the candidate who is rude or thoughtless, or has rude or thoughtless workers. As Gordon Brown discovered when he called a woman a bigot.
I wouldn't vote Green for many more reasons than a random activist's rudeness, but it would certainly factor in to a decision if it came down to a difficult decision between two otherwise good parties or candidates.