What do you think???

I think cheating is the worst thing that people can do, but what if the person who was cheating or going to cheat was a good friend? Do we change our thinking...I don't think so, but what do we say to them? Even if they physically haven't cheated with someone but emotionally cheated it is just as bad. Then I pose this question what if you like someone who has a girlfriend or boyfriend but you flirt with them and they flirt with you but continue there relationship what does that say about you? I see this all the time, but recently I have seen an interesting situation that has brought on all these questions. My question to you is where do we draw the line since it seems to get so blurred all time.