AAARGH!

Okay, from the top: "brick shithouse" and "brick house" are the same thing; the Commodores just couldn't say "shit" on the radio. Either phrase means the same thing, whether applied to males or females (though it is interpreted differently for gender): "well-built". It was a compliment to female form *long* before it was shortened.

The actual origin is obvious when you think about it: most outhouses were made of wood, so a brick shithouse is unusually well-built. Despite the presence of "shit" in the phrase, it is IN NO WAY an insult by itself. (The notion that "brick house" is the original form because the metaphor corresponds with "stacked" is false. It was a nice bit of back-formation.)

So, translation: Madonna says that one of the reasons Gaga has a gay following is that she looks like an outsider (something she has in common with Madonna, btw); she does not sport the tall buxom blonde Amazonian look of someone like Spears. It's not an insult to Gaga. It's not an insult to Britney. It's an astute observation, and that's all it is.