This of course is why coalitions are fundamentally undemocratic and an abomination in any civilised system. What it means in effect is that an MP needs to vote in a way he or she believes is wrong and damaging to the country, in order to have another MP vote the way he or she wants on another issue (although that other MP believes it to be wrong). This is simply unacceptable. Any candidate who would even consider entering a coalition, is ipso facto unsuitable to be an MP.
MPs vote against their beliefs all the time, within their same party. They don't need to be in a coalition to do it. because they follow a party whip system. A perfect example is that a majority of MPs were not in favour of leaving the EU, yet the vast majority went against their beliefs and voted for it.
Let's take our MP for 2015-2017. The data's all public and easy to read.
http://www.publicwhip.org.uk/mp.php?id=uk.org.publicwhip/member/41020&showall=yes#divisionsOut of 419 votes he took part in, he rebelled from the party line 3 times. That's 0.7% of the time. It seems highly unlikely the other 99.3% of the votes, he believed exactly the party line was spot on. Even in one party there are many beliefs and viewpoints. No. He toed the party line for at least some of those times.
As an aside, an anti-coalition attitude of many in this nation got us to a position where 63.1% of the population didn't vote for the party that formed the government in 2015. It's why the SNP got 4.7% of the vote but got 7.69% of the seats, yet Ukip got 12.6% and got 0.15% of the seats (aka 1). It's why all the power is in a handful of marginal seats, whilst those in safe seats really can do nothing. (And until I moved to Marple, I'd lived all my life in safe seats.)
Our voting system is not a fair one by any means.