Arguments from intuition, in addition to being unscientific, are illogical. As the basis for making objective judgements about the world, they are utterly unsuitable, because they themselves are subjective and not shared by everyone. Furthermore, they can very easily be wrong. While intuitions do sometimes stem from true and innate knowledge about a subject, familial or other social pressures can generate them with just as much ease.
One cannot communicate a 'feeling' that something is right or wrong to others to the extent that the others can 'feel' it in the same way. Thus, basing an argument against, say, homosexuality on an intuition that homosexual acts are disgusting is both illogical and useless, as the only ones whom the argument will convince are those who share that intuition, and who thus already agree with one! I have read just such an argument, and it did not hold up at all under even a small amount of rational questioning.
Of course, many people may argue that their intuitions are universally shared, and that anyone who claims otherwise is deceiving themself, but this does not really work either. It would be very easy for the anti-homosexuality arguer mentioned above to claim that anyone who apparently does not find homosexual acts disgusting is either lying in order to support a misguided agenda, or is homosexual themself. This is obviously ridiculous, and it can apply to other concepts as well.
Lastly, some people may say that their intuitions are at least more likely to be right than wrong, and that even if they are wrong they will do no harm, whereas if they are right but do not act on their intuitions, harm will occur. Unfortunately, this depends on a subjective definition of harm, which all too often rests upon the very intuitions in question. Re-using the homosexuality example, a supporter might claim that allowing homosexuality (against their intuitions) would cause great moral harm, but preventing people from acting on homosexual wishes does those people no harm, because they can always be heterosexual. Naturally, this is fallacious, because homosexuals are not heterosexual - but because of their intuitive 'knowledge' of the matter, people may not recognise this.
