On one hand, an enamored person is oblivious to the many flaws of the one who they desire. That makes the lover a pretty deluded creature from this standpoint. I can't disagree with that. It often happens to be the case.
On the other hand, you can't say that a person will always stop loving someone if they "faced the truth", so to speak. If love is true, it will endure all disillusionment, and while many would say that such a person just continues to delude themselves further, I'd argue that this is indeed a sign of true love. This may very well be the real opposite of prejudice - since the person continues to love someone despite knowing everything about them. Often they just happen to know where their love stems from. In case of mature love, feelings are often on the border between the rational and irrational, while the initial passion is often fully irrational. True love can be a special form of insight, a feat of seeing something others cannot see. Not only this means that such love is not a delusion/prejudice - it means that pure love can be honest and quite transparent. Still, wouldn't disagree that this is more of an exception than a rule, considering the reality of things.