If he thinks it's wrong to step on bugs, that's his prerogative. You obviously think it's OK, and that's your prerogative, so he has no right to say you're inhumane, and it's certainly uncalled for to call you a "white bully."
See, it's not really black and white though. When it comes to right and wrong it just depends on how much value one places on something. If someone cuts down a tree most people won't take notice, while some will chain themselves to it. As long as humans can think for themselves they will never agree on a moral compass. Some don't have a moral compass. Most agree that intervention is sometimes necessary, but intervening for a few ants is excessive, and name calling certainly won't change anything either.
"Do you think stepping on bugs is wrong - why or why not?"
If I see an ant wandering around by itself and happen to squish it for no reason at all, I do feel an ounce of guilt because it was so small, harmless, and defenseless by itself. On the other hand I might not feel much guilt for treating an entire yard for bugs simply because I don't want them there anymore. I used to try and burn them with a magnifying glass, which was very difficult. Those little bastards run fast. What I did do that I feel bad about now, is pour salt on snails, or chuck them at the ground to crack 'em. I'm a little undecided on the morality of that one. They're just snails, but I definitely wouldn't do it again, although the salting effect is still a bit fascinating. I wouldn't be appalled to see a kid doing it, but if it was my own I would suggest that it might be suffering.
"But If I'm stepping on this kid's uncle bob or grandma jane, is that really such a bad thing?"
Lol...no. I'm open to reincarnation, but I don't really think bugs are included, and if they are, well, that's a bugs life.