Not for the first time in France, I find my moral compass spinning out of control as a result of a bitter row over immigration. It all starts with a recent proposal from the ruling centre-right to introduce voluntary DNA tests for would-be immigrants who want to prove their kinship with family-members living in France. It is presented as a practical measure that will accelerate the application process for people in countries where official documents are regarded as untrustworthy by French immigration officials. Beneficial, in other words, to genuine applicants for family-reunification because it will speed things up and exclude fraudsters. But for opponents, the idea verges on racism. They say the DNA tests -- in theory voluntary -- will in practice become the norm, because those reluctant to take them will be assumed to be bent on deceipt; that it plays to the stereotype of foreigners trying to outwit the system; and that it creates a dangerous notion of the family and nation based solely on genetic affiliation. The government pleads that 12 EU nations practice similar tests, and they concede that the state should pay for all tests so there is no discrimination against the poor. But the left remains up in arms. Why do I feel uneasy about all of this? I suppose it is because the reaction of the measure's opponents has been so unutterably shrill. They may well have a good case -- but in my view they do it only harm by suggesting that the only people who could possibly support the measure are closet racists. The language of the debate has become virulent. Backers of DNA tests are made to think they have committed an extraodinary moral offence, that it is all the first step on a slippery slope leading back to Vichy and the gas chambers. Why is it that in the 12 other countries which have the measure, the same vituperation was not flung about? Why is the British government not accused of abject racism, nor the Lithuanians nor the Finns? Is it because the French feel they must obey higher moral standards? Or is it because they are afraid of their own dirty past? It is most disconcerting. Personally I am lost. I rather suspect the DNA tests will make little practical difference. But I cannot claim to feel moral outrage. Maybe there are a lot of immigrant families who would welcome it. Does that make me morally deficient?