There were no excuses made by me. I merely stated that in my experience children from families where both parents work outside the home are noticeably less well-mannered and well-adjusted. There are also several studies which suggest that children in full-time daycare are markedly more aggressive than children raised at home.
I'm glad that your single mom was able to do a good job. That, however, does not address whether that is the best way to raise children for most people. And you will have a very tough time disproving that, in general, the best way to raise children is in a two-parent family where one parent devotes his or her time primarily to caregiving.
While I'll grant you that it's harder to do a decent job raising a kid if all parents (leaving the door open for single moms here) work I think, especially in today's victim oriented society, it's dangerous to leave the door open to that being a why the bad parent can use. In the end if a parent (or preferably both parents) puts some real effort into doing a good job raising their kid the obstacles won't matter. If kids turn out bad it's because the parent(s) didn't do their job, there's probably a list of reasons the parent can bring up, some of which might actually be valid, but in the end the only real job a parent has is raising the kid right and anything they let keep them away from that job is their fault.
I don't doubt those daycare studies for a minute. I did a bit of daycare (my mom hated it, but it was unavoidable, dad was making a play to end support and letting me stay home unsupervised wasn't an option for a while) and it's crazy. The best way I could describe daycare is think of a prison riot done in half size with less lethal weapons. Because the people involved are not teachers there's nothing to do but play with the toys that are generally broken and there aren't enough to go around anyway; with no focus and no one really in charge it's a madhouse. I much prefered going home I'd just turn on the Barney Miller reruns and do homework or read.