My mistress' eyes: Personal Reflection

I'm going to take a stab at the meaning of this poem. First off, literally all the first 12 lines state all the imperfections of the speaker's mistress and how he doesn't like her. Then he goes on to say his love is rare and great. Why discuss everything that you hate about someone and then go on to tell them you love them? That just seems to go against the normal way of things. However, I think that the meaning to this poem could be that imperfections shouldn't matter. The speaker describes all the flaws in his mistress' physical being yet never says anything bad about her spiritual characteristics. Through this, he creates a sense of flawless spirit among the woman and conveys that physical imperfections should not determine love.