Actually, the question that matters to a lot of people is not this one exactly, but rather the one about bad minority parties. Yesterday I said that AV doesn't give the BNP a better chance of getting its candidates into Parliament. Today I want to ask, what if it did? Or what if it gave BNP first-choice voters more influence than they are likely to have under FPTP?
First, this thought experiment. Suppose that we have in place the electoral system that you consider to be the very best available; and let that be, for familiarity's sake, FPTP. OK, so for a long time no BNP candidates are elected to the House of Commons and you are happy about this. But one day, in one constituency, a BNPer is elected - with 35% of the vote, let's say, to 31% for the nearest rival candidate - and it bothers you. Still, do you press for the result not to be accepted, for it to be overruled by someone or other, or for the candidate to be abducted maybe? Let's say, for the sake of argument, that you don't press for any of these things. As a democrat you accept that the results of the democratic process may sometimes be disagreeable to you, and you work towards seeing the constituency in question returned into better hands at the next election.
However, in line with the argument I made on the question of when, if ever, criminal acts are permissible on political grounds, your commitment to democracy is not without limits. Suppose, now, that a fascist party of extreme virulence has grown and grown and FPTP is on the point of delivering to it a majority in Parliament. You are not only a democrat but also a liberal and have real fears about the country's future, fears well grounded in what this fascist party on the point of power has threatened, which includes policies of an openly racist and gravely human-rights-violating kind. You have at your disposal (I suppose further and somewhat fancifully) the means of aborting the electoral process and of instituting a benign liberal despotism that keeps the fascists out of power and does no seriously illiberal damage. You go for it.
On the basis of this story, you may be seen to have a commitment to democracy that extends so far but not to the end of the world. You will put up with one or two BNP people being elected to the House of Commons, but if need be, in order to block the triumph of fascism and the further consequences of that - assuming that you can - you prefer to see democracy set aside.
Back now to reality. Well, kind of. Imagine that you are faced - as a democrat - with a choice between two electoral methods, never mind what they are. EM1 you judge to have advantages over EM9, in terms of representivity, fairness, stability and nearly everything else. EM1 is all-round better than EM9, you think - except for only one thing. EM1 might slightly increase the representation or influence of a minority party that you judge to be somewhere between unpleasantly annoying and hateful and dangerous. Should you reject EM1 on those grounds? But if your commitment to democracy means anything, is an electoral method to be rejected just because it accommodates results which you don't like? What's the difference between this and simply outlawing the party whose influence you don't wish to see grow? What I'm asking is, how much weight should we give, anyway, to the consideration that an electoral method might increase the influence of a party or parties we judge to be pernicious?