Men or women who feel the need to cheat or string along others has a lack of self-esteem. The attention they are getting from someone else only builds their ego. A person should be confident enough in themselves not to need the attention of others to feel good about appearance or their ability to be physically attractive to others. You are sexting as a prelude to a sexual relationship with that individual. By saying, I'm never going to meet with this person is a line of bull, because you know the first time the conversation gets all hot and bothered you will be running off to have sex with them. If you are willing to cross the line of sexting, you will be willing to cross the line of having a sexual relationship with that person too. You don't have to be having sex with them now to be cheating if you are sexting. Eventually, things will lead to a sexual relationship with the other person. It's considered cheating because you are talking sex with another individual while you are vowing to be honest and faithful to your partner.
You have to look at it this way... if you are texting someone and hiding it from your partner, then you know deep down what you are doing is wrong and your partner WILL react negatively towards you and most likely dump your ass when they find out. Saying you don't care if they were doing it is an excuse to validate your own behavior. When you know deep down, your heart would drop to your stomach if you happen to find out your partner was sexting with someone.
So do yourself and your partner a favor, save them the heartache of your betrayal and be faithful. You really have to ask yourself the question "Is this person worth losing the one I love?" Apparently not if you are not willing to leave your partner for them and have a relationship with the person you are sexting.