That's a dramatic way to put it.
At the time Baldur's Gate was created, there were not many games that gave you the option of being evil. Playing "evil" was probably considered to be something of a "joke" play through added because of the alignment system and to give negative consequence to 'bad' actions.
Then why add it at all in a game based on a tabletop where creative roleplaying, regardless of alignment, can yield rewards. This seems like a copout idea of their intentions, or, if accurate, a copout on their part.
Yes, awarding XP for "good" or "evil" behavior is an odd thing in itself. Unless the decision resulted from a skill check by the character, experience comes from dealing with the consequences of the decision, rather than from the decision itself. But then I suppose it could be viewed as an abstraction of sorts -- payment in advance for the consequences of your choice.