Labour party had a golden opportunity and they fucked it up. Don't blame people for voting Tory, blame the Labour party for not doing a good enough job to convince voters. If anything this was most probably the easiest election for them to win, yet they massively screwed it up.
Labour supporters should be more angry at their own party for not getting enough votes, for doing a piss poor job of convincing people, for not dealing with all the issues that cropped up around in a way that gave people confidence to vote for them.