If you think that people are stupid to keep voting for something which doesn't represent them doesn't that also suggest they are too stupid to vote on major, complicated decisions which most people (and I include myself in that) don't understand in enough detail to make a well informed decision? Especially when there ARE alternatives which would represent their views more closely like the Greens or UKIP or whoever, but because of our FPTP system people get into tactical voting and don't vote for the party they want to rule. That is partly a problem with the system rather than the people but we had a chance to change the system to one which demonstrably yields more representitive results but the people rejected it because it was a bit complicated.
Either way, people are, on average, a bit stupid so while self-determination may be a nice theory, the reality is that stupid people sorting things out for themselves sounds like a terrible idea.
The majority (in the sense of over 50%) didn't vote for the Tories but more people voted for them than any other party
http://www.bbc.co.uk/news/election/2015/results
Again, that's a flaw in our system. 12% of people voted for UKIP. 1 in 8. And they have 1 out of 650 MPs. Whatever you think of UKIP that is a lot of disenfranchised people. And I don't think voting that way does mean they approve of inequality and injustice, that would only be valid reasoning if you (or 'the people') thought that the alternatives would deliver equality and justice.
It's a similar argument to the Arsenal one - if everyone stopped going, stopped buying the shirts, stopped subscribing to the TV channels then the board would get the message. If everyone stopped voting then the powers that be might get the message that the system needs to change but the reality is neither will happen so most people figure we might as well get on with it and vote. The alternative only works (if it would work at all) if everyone signs up and there's no sign that will happen any time soon.