Plenty of people are a net negative on the world, so yeah, your threshold may vary. Someone who earns money at the cost of another's livelihood? Guy who drives recklessly and might kill someone? Someone who makes a point to not tip just to ruin a person's day?

Granted respect isn't a great word for it, I say fuck all three but wouldn't go so far as to say assassinate em. But Trump? Yeah that's a bit past that threshold.