Now maybe my view is biased, but here is my view, and I'd love to see yours on this topic.
   So the whole "sex addict" idea is someone is so addicted to sex they'll abide their marriage, life, family, ect. I'm gonna stop here and call this Bull Sh*t. When a man or woman is commonly caught having an affair they usually blame it on being a "sex addict." And I don't believe it, I grew up with a stepfather who walked out for some other woman who is a complete skank. Point being, he cried wolf, in this case, sex addict. And no one believed him. Not surprising.
   Now  I can understand, "Yeah, sex has a great feel, to be loved, it can be addicting-- yo," and I completely agree sex can be like that.  However to the extent of being addicted? I don't think so. 

Maybe I don't understand what you are fully saying, but are you saying there is no such thing as sex addicts?

It may seem that blaming the whole thing as being a sex addict is less than you would prefer, but it is certainly a real thing, and a real problem. Addiction can literally happen with anything, but it is usually only given widespread familiarity with alcohol and other substance abuses. You are saying that you do not believe it, but it is definitely there.  Some people can control it better than others, but some people have lesser levels of willpower, and it results in them seeking more sexual interaction extra-maritally, for which they can not easily obtain with their partner as frequently as their urges come. It is not a good reason to walk out on anyone, and I am sorry for what happened, but being addicted to sex can definitely happen, and will happen to people. Your stepfather is definitely in the wrong here though, either way you look at it.

BluemageKyle :

"My boy has ADD" is abused, "I need to be gluten free" is abused, and "I'm a sex addict" is abused. All those disorders are real, but they occur less than people think they do. You're stepfather is probably not a sex addict, he's a cheater. Sex addicts have sex/masturbate twice a day at minimum. I've seen articles that won't call it sex addiction unless it's over 20 times a week, which would make an average of 3 times per day. The only real way to claim "sex addiction" is if the spouse is understandably refusing the twice a day sex. If he wasn't needing it, he's not a sex addict; he just has issues with fidelity. 

I think sex can cause an addiction, but being unable to break such an addiction is most likely due to not having the willpower or determination. I feel the same way towards most addictions (drugs, food, laziness, etc.), and most of the time the addiction is caused by not having the willpower to resist it in the first place. People start doing drugs because they couldn't resist starting to do them in the first place, or doing them the second time, third time, and so on. So yes, I believe sex addictions do exist, but the people with them are normally weak (no offense to you if you have a drug/sex addiction, but you should really evaluate your life).

The definition of sex addict isn't masturbating or having sex twice a day.  It goes far beyond that and it is the physical manifestation of obsessive or compulsive behavior.  It's not just that people have a lot of sex.  My wife and I have a lot of sex.  When people endanger their lives, their relationships, their bank accounts, their employment, their kids, and actively disrupt their life activities, they can start thinking about being called a sex addict.

It happens.  Sure people blame it when they're at fault.  That doesn't mean it exists or real sex addicts should be discredited.  Some people may be dealing with it right now and looking at you with sadness because you can't and won't accept who they are.

warmaker :

I was just trying to illustrate the extreme. Addiction is super complex, and I'd rather not write a textbook on human psych =)

what it REALLY is, is just being weak. the same as any other addiction. you achieve a sensation or thrill you do not normally get to experience, and youre so weak that you cannot hold yourself back from it. been down that road, and the cure is as simple, in EVERY case, as to just man up and stop chasing poon/dope/booze

Anything that causes any form of happiness or satisfaction has addictive qualities. Sex addiction is certainly real, and incredibly wide-spread and popular. I still don't understand why it can be used as an excuse though, everyone should be able to control their urges. If they can't, then it's an addiction. Your step-father is a jerk, and although being addicted to sex could be one of the reasons, it certainly wasn't the sole reason. I don't know his life or his situation at the time, but it is possible that he wasn't happy with his life and "fled" to another women that made him feel more secure and in control. Either way it was a stupid move. If he was a sex addict, then shame on him for obvious reasons. If he was unsatisfied with his life, shame on him for running away from his problems instead of facing them. 

BluemageKyle :  I think you are on to something here guy.  Aren't we all really sex addicts.  As we are genetically programmed to continue the human race and that means seeking out a partner.  Using your ability to give your sleazyness and inability to control yourself seems kind of like an a excuse rather than a medical condition.  Sex addict my butt, more like you just wanna do what you wanna do and have a "medical" excuse for doing it.

Sex releases chemicals in our body that produce happy feelings... just like other addictive substances. Some people react to those more strongly than others. Addiction is not a weakness, it is a disease. Those people actually have a problem, and calling them weak and dismissing their problems just makes you look like a world class jerk.

That said, addiction in any form, and especially sex addiction, is never an excuse to destroy your family. I agree, your stepfather was full of it. Tiger Woods was also full of it in my opinion (he just let his celebrity get to his head). If you have a problem, get help. Simple as that.