While there was certainly a racial element in the wake of a dismantled AA system in Texas, that's not what closed the deal. The 10% rule enjoyed widespread support in the state because with it's rural population in excess of 20%, Texas isn't as urban as many states.
One of the downsides to rural living is the school systems are often by necessity more limited than their larger urban counterparts. I was living in a small Texas town of 882 when this was debated, as was oft pointed out, our high school was too small to offer AP courses, only offered a foriegn language when a teacher was available, didn't offer calculus etc, but our kids were competing against urban kids who did have access to these things.
So for good or for bad, rural Texan's saw this as a chance for their kids to have a shot at good schooling, and THAT closed the deal. The author, a Houstonite, obviously didn't get it.
Some kids are getting accepted who clearly are not cut out for the intense academic pressures of those universities. It does, however, keep minority enrollment to levels roughly equivalent to pre-Hopwood numbers.
But the real negative effects are seen on those students in exceptional suburban high schools with overwhelming numbers of kids that come from families of highly-educated and intelligent parents. The kids are going to be largely superior students themselves, but it's impossible for all of them to be in the top 10% of their class. 90% of them will have a very tough time getting into the University of Texas or Texas A&M.