While I think this is abusive, I can see why people who are okay with spanking would be okay with this too. The hot sauce is probably more painful than spanking (and the pain won't fade as fast), but it's less demeaning, doesn't have an weird sexual connotations, and if I'm not mistaken, is less likely to cause injury. Yeah, the premeditation aspect is creepy, but according to pro-spankers, spanking is supposed to be premeditated too. They say, "Never spank in anger." The hot sauce is harder to use in a fit of rage. So if you want to inflict physical pain upon your child as a punishment, isn't hot sauce the more logical choice?
(Though if this becomes a popular discipline technique--God forbid--I suppose in like 20 years, BDSM people will be pouring hot sauce in each other's mouths....)
Many pro-spankers use the argument that they're hardly causing the child any physical pain but rather the punishment is the emotional pain that comes from the idea that their parent would do such a thing to them (they don't refer to it like that). They'll say they "barely tapped" the child. But I can see them doing the same thing with the hot sauce. "Oh, it's not that hot. Stop that crying or I'll give you something to cry about!