Democracy and the prisoner dilemma

David Cameron has put his foot down over the European Court of Human Rights ruling that the U.K’s blanket ban on prisoners voting in elections should be revoked, stating in the House of Commons:

“No one should be under any doubt — prisoners are not getting the vote under this government,”

He has said before that the thought of prisoners voting makes him “physically sick” and there is no doubt that many on the right of the Conservative party have particularly strong views in this direction.
It is also true that the idea of ignoring the European Court is of itself attractive to the euro-sceptics and large sections of the public so his rhetoric may well be designed to strike a populist chord as well as being a genuine reflection of his views.
However, and this may be a contentious view to some, I think the antipathy to prisoners voting is fundamentally misguided and a misreading of the balance of rights and responsibilities in a democratic nation
To express disgust at the idea of convicted offenders voting is to ascribe the electoral franchise the status of a privilege, something that completely goes against the principle of universal suffrage. Voting was a privilege when only the landed gentry could participate, it was still a privilege when only men were allowed to do it. In a modern democracy the ability to have a say in who governs the society you live in is a universal right, which should not lightly be denied any adult citizen.
Obviously we do deny prisoners many rights, not least the right to liberty, but more than a right, exercising your franchise is a responsibility and in my opinion should be a moral obligation. Participating in the democratic process is a duty of citizenship and those people who do take the time and trouble to become informed, have opinions of whatever hue and then demonstrate that at the ballot box are engaging constructively with the future of the nation
It seems to me that the worst signal we can send to a felon, someone who by definition is either not engaged with society or is destructively opposed to it, is to tell them that they cannot be a part of the process that defines it.
Rather than deny these people the vote, many of whom have probably never bothered anyway, we should in fact insist that they do. Teach them civics, engage them in political debates, educate them in the democratic process and then put a ballot box in every prison and require them to use it.