Can someone who purports to favour a position really be said to favour of it when he can concretely identify no circumstances in which his policy is beneficial?
I think saying "I'm in favour of X in concept" or "in principle" is basically just a pose.
People who adopt this position in relation to European integration (e.g., saying "the general concept is a good one") therefore do not need to argue that the actual existing EU is a good thing, which they admit it is not, nor must they evaluate any concrete hypothetical form the EU might take. Indeed it is possible to proclaim oneself in favour of the EU in the abstract, but unable to identify a single, concrete form the EU might take which might be acceptable to anyone.
Argument by analogy is never conclusive, but it's certainly illustrative, and the analogies aren't very favourable ...
Saying "I favour X in principle" is analogous to saying "I'm not a racist, I just don't like individual black people.", Neil Harding's titanium-skulled commitment to ID cards "in principle", or "Communism was great in theory, but we never got actual existing communism anywhere.", which is particularly offensive (communism is even worse in theory than it is in practice, and we got enough examples of actual existing to communism to put all but the most hardened genocidal maniacs off the whole business for millennia).
Consider the mathematical analogues of "in favour in the abstract but not in the concrete": someone could say "I am happy to pay a higher train fare on any day of the month, except even-numbered dates and odd-numbered dates". Now it can be proven that all positive integers are either odd or even, and thus the set of days in which the supporter, in theory, of higher fares would be prepared so to act is the empty set. One may go further and define one's position in terms of an obvious contradiction: "I am prepared to pay more on any day whose number is one greater than itself", which yields the empty set for a different reason. Of course, you can't away with being so obvious, but might define your position in terms of an unproven conjecture, "I shall pay more when the number of seconds elapsed since 1970 is an even number inexpressible as the sum of two primes".
This post is reasonably heavily edited from the original