The problem with the UK legal attitude to rape is that two adults who get drunk and have sex do not do so on an equal footing. Both could conceivably (in the eyes of the law, if not the general public) be drunk enough as to no be able to give consent, yet could still end up having sex. In this instance the male could be liable for rape, and the female could not. The same would be true of two men who had sex - the man who does the penetration could be liable for rape, and the man who was penetrated could not.
Most people would blame a person for being mugged, at least partially, if s/he had walked home through a known rough area, when alternative routes or a larger group to walk with were available.
The fact is that everyone knows that clubs and other alcohol-fuelled venues are places where many people come to look for a sexual partner. Everyone knows that drinking alcohol lowers your inhibitions. But the law does not seem to recognise that a man's inhibitions are lowered by alcohol (and hold him responsible for his actions when in this state) despite recognising that a woman's inhibitions are so lowered (and they remove her responsibility whilst in this state). Of course, a male rape victim may have his incapacity due to voluntary drinking recognised, and therefore not be held responsible for sexual activity in which he is involved, whilst the man who penetrates him may be equally unable to consent in terms of how much he has had to drink, but will still be held responsible for his actions.
Even if you take the example of a sober man having sex with a woman or man who is clearly too drunk to consent, the person is almost definitely responsible for becoming so drunk. They bear no responsibility for the rapist's actions, but they are responsible for being drunk. If the rape would not have occurred had they been sober, then most people would make the link and say that their intoxication leads to their partial responsibility for what happened to them. A drunk person doesn't want to be raped, nevertheless intoxication invites rape, if you take that to mean that a person has put him/herself in a situation where any sex will not be consensual.
Another problem is that many people would not consider the above sentence to be true (although I would argue that it is, in terms of the law) and many men would not think "this woman/man is drunk enough that she cannot consent" but would think "this woman/man is drunk and therefore cannot consent". Of course the exact point at which intoxication is sufficient as to render valid consent impossible is not easy to define, but rather than being cautious and questioning whether anyone obviously under the influence of alcohol is able to consent, many (not:all) men instead assume that the person is able to consent until (or even in spite of) overwhelming evidence to the contrary, such as an inability to walk, or unconsciousness.