Well, you're conflating two issues there - taste and opinion.
As to suggesting that a person's taste can be 'wrong', it's you who is drawing that inference from what you're reading, and mistakenly thinking it's therefore implied in what you read: it's not. Taste can't be 'wrong' any more than intelligence can be 'wrong'. Taste, however, is a characteristic and therefore it's an indicator. Somebody who has a taste for Marr's songs isn't wrong - they're just lacking in an ability to distinguish good lyrics and melodies from bad, or else they just don't care that the lyrics are shit and the melodies are uninspired. Which is fair enough.
As to the notion that opinions can't be wrong, well that's your opinion and it's wrong. If someone expresses the opinion that all actors are homosexual, for example, well that person's opinion is wrong. To think that opinions can't be wrong is... well, I'll be more polite than you were... it's not very bright.
No, sod it, I'll call a spade a spade - it's f***ing stupid.