Mr Hughes thinks Lib Dem backbenchers should have a veto on Coalition policies. Some would say only if Conservative backbenchers as well can have one, to be fair.
The truth is simple. If all Lib Dem backbenchers vote against a Coaltion government proposal, even with Labour support, the government will still win the vote.
If a large number of Conservatives rebel, but Labour supports the government, the government will win the vote.
It is only if more than 40 Conservatives vote against the government and Labour opportunistically agrees that the government might lose.
Democratic politics is about numbers as well as arguments.