I agree being nice brings disrespect as consequence on most situations in this modern world. The dark side inside human beings is flourishing and becoming dominant these days, while the bright side is being suppressed.
But if you stop being a nice person, you are going to do exactly what the dark side wants you to do, so you will become one of those fools: just another asshole in this modern wicked world to cause pain to your fellow human beings.
People misunderstand politeness with weakness, and that is why they try abusing a polite individual. Just be proud of being a nice individual. Give others the benefit of the doubt. But as soon as you identify they are taking advantage of your politeness, impose limits, get away and maintain only essential necessary contact.
Relationships must be reciprocal, healthy and uplifting. If you see they are being abusive, toxic and harmful, stand for yourself and don't go further. Respect yourself in first place.
Being nice sometimes is good but most times it's disastrous and bring disrespect,some people due to good upbringing are nice because it was instill in them from child.while most people that disrespect people is due to hatred,anger and unstable state of mind.also being nice to people doesn't mean they will not disrespect you.just do what does not trouble your conscience .
There is no need to keep toxic people around you because they could be the source of disappointment to you and make you feel very sad about your personal joy. We all need to have a personal joy that will keep us cool whenever we find ourselves in problem.
Most people that disrespect others are really having mental issues which could have been due to the problem they might have had in the past that had led to their prolong issues with other problems.