I see both sides.
I think if you actually listen to the lyrics, you can hear she's celebrating all mothers. I think the issue is that the general public may be hung up on the song title or not pay that close attention to every single word because there has been such a negative connotation associated with the term Baby Mama. I also agree with someone who stated that it is very risky for someone like Brandy to try to challenge or change that connotation.
However, none of that takes away from the song for ME It's still a great song. I love the production and her voice is soaring.