- Ok lets say that someone in your life (lets say a freind) is a danger to your purity- and I'm not saying this person is a silly sally or something but things they do and say that they don't know the efffect it has- is ok to ignore that person at least temporarily so as to protect your purity. And if you promised to go hang out with that person but now realised it might not be such a hot idea is it ok to go against.
and explaining the situation to that person would be really weird and awkward and strange and basically a big no-no.
Now, some people are able to remain friends with a person like that, even if the person continues to sin in that way, because they do not easily fall into another man's sin and because the scandal of the sin does not outweigh the good in the other person (we're all sinners, afterall).
However, other people find themselves falling into the very sin their friend commits because, by being around that friend, they become desensitized by the sin and more likely to commit it. If you are likely to fall in this way, or if the sin is such that it is just too scandalizing for you, then you will need to find new friends that do not have such a negative influence.
The tough thing about conversion is that it means changing your whole life and orienting it towards the Lord. Since we are not solitary beings, this often impacts other people as well.