Rather than trying to tell you why voting for another party is a bad thing?
I had a Labour campaigner come to my door yesterday.
Currently, I'm a Conservative supporter but my views are fairly liberal - i think the current Labour are too left wing but they have some policies I could get behind, so I was happy to have a chat with him.
However, the first thing he did was hand me a leaflet which showed all the shitty ways the local Conservative MP had voted in recent years. Fine - some of his views are a bit prehistoric and I can't get behind them. The campaigner talked to me about these posts.
Once he'd left I noticed on the other side was some ways the Labour candidate would vote, which the campaigner hadn't even mentioned.
We then moved on to Brexit (obviously) and I asked how I can be sure Corbyn would negotiate the best trade deal before a second referendum, without knowing which way Corbyn himself would vote. The campaigners answer was "because he said so." Because, you know, we can always rely on politicians to tell us the truth 
.
He then went on to say the Remain is the best option anyway and that everyone who voted Leave is a Xenophobe because nobody had a good reason to leave other than immigration. I told him you can't exactly label half the country as Xenophobic because they don't agree with your opinion.
Every time I tried to steer the conversation towards policies on other things, he'd attack the Conservatives rather than try to help me understand Labours approach.
Am I being unreasonable to think that unless you're going to attempt to promote your own party, there is 0 point in canvassing?
He was of the assumption everyone will vote either Conservative or Labour. To be honest, if I was on the fence, his aggression with regards to democracy would have swung it the other way for me.