I have a toxic friend. She is smart, amazing, and fun! She does have an issue that requires medication and impacts her choices. There is much empathy for her plight and she has done a lot of damage to her own life. Toxicity is a way of thinking that is associated with fears the person has not dealt with. Such thinking causes them to over react and seek to gain advantages where they should not be. In the end people become alienated. It can be extremely taxing to deal with a toxic person.
Over the years I learned that you simply can't change the way people think. As a matter of fact, most people can't even change the way they think either. These patterns were put in place throughout their lives and it is doubtful anything will change thereafter....unless that person is exceptional enough to self-reflect.
Here are a few things you should consider.
1.) You can't control other peoples behavior but you can control yours. Understand that what people do and say is a reflection of them and their beliefs.
2.) People have all types of reasons to hate on someone. Sometimes you actually do something wrong while at other times it is in them. When people act this way ensure they respect your boundaries and be positive with them.
3.) Because things do go wrong and people do stop talking to each other it is best you stop and think before acting. Don't just jump in there and spew hate out of your mouth. Think long-term and then choose your response.
4.) Be aware that many times things won't get better and the relationship is over. Leave with grace, saying good things, and wish them well. If they are very bad people then just say nothing and move on.
5.) Self reflect and learn from each situation.