Time to clear up a few things
I never said it was good, I said it was legal. He hit the right area. But this could bring change in Corporal Punishment laws throughout the country, and those who were brought up in sanely God fearing strict families are not gonna like it one bit.
Sorry, but 16 is WAY too old for corporal punishment, and that wasn't punishment, it was a flat out beating. Not called for at all.
That being said, stealing IS wrong, and lying and thievery are my two biggest issues when dealing with kids (or anyone else) but he was way over the line. He could have dealt with it far better than he did.
I think he crossed the line. Yes, Texas allows for corporal punishment of a child; however, 17 lashings with a belt? Also, agree with Toasted re what he was saying. I think, for me, the most horrifying part of this whole incident is that this man sits in judgement of other parents, deciding if they are fit to raise their own children. It would be interesting to see how many times he has terminated or otherwise limited the parental rights of other parents who have done something similar.
I understand that while there will never be criminal charges brought (statute of limitations) and maybe are not even appropriate to the situation, social services is investigating because there is another minor child under his care and custody, at least part time.
By law Corporal Punishment can only be used on minors, 16 year olds are minors. I got lashed 20X at 17. My brother got the paddle at school at 14. Doesn't matter, if you live under their roof, they can run the house however they legally see fit.
The other thing that disturbs me is from what i understand the girl suffered from CP as well! Great! So you probably get made fun of at school and whenever you screw up at home you get this! ugh! Life really sucks sometimes! 
As for cerebral palsy, that disability deals with motor skills, not a mental deterioration or retardation. I saw news spots of the girl today being interviewed and walking, you can't tell she has it. But I do believe she does.
His words used were most definitely WAY OUTTA LINE! Even when I was spanked at 17, I was screamed at, but not denigrated with cuss words.