Had a labour supporter on my doorstep last night trying to say the same thing. Unfortunately I don't think it's a very good tactic if you want someone to vote for the party you support. It's sad if someone thinks that if you vote Tory you cannot empathise with others or that you are heartless. Some of the most generous and kindest people I have ever met have happened to vote conservative.
In summary, normal people who want to vote labour have my respect, militant union types who bang on about the common man and blame the Conservatives for all the ills of the world can do one as far as I'm concerned. Certainly aren't going to change my mind by getting people like that on my doorstep.