Since 99.81% of all black people in Texas were slaves then the odds are that if your ancestor ever met a black person then that person was likely to be someone's chattel. Thus he no doubt saw slavery as the right and proper place for a black person to be in, and would possibly resent any attempts to change what he saw as the natural order of things. But your ancestor was not one of the 28.5% of all Texas families that owned slaves. Those families brought a great deal of wealth to Texas and it's not unlikely that your ancestor earned a part of his living selling goods to those slave-holding families. It would certainly have been in his best interest to help protect his customers. So those are some of the ways your non-slave-holding ancestor benefited from the institution.