Well, it comes to a definition of terms. The best definition of addiction that I know is: compulsive behavior that one can’t control despite full awareness that it’s harmful.
The chemical “high” from sex (including the times leading up to it and following it) can be very close, if not identical, to the high from many drugs. While it’s true that sex “addiction” may not produce the chemical dependence of opiates, the compulsive behavior can be similar to that produced by cocaine and amphetamines, both of which are acknowledged to be addictive.
Having said that, I should clarify that “addiction” to sex is NEVER an excuse for any harmful behavior. IMO, all individuals are fully responsible for their choices and actions and addiction of any kind doesn’t free us from that. My main point is that when it comes to treatment, I think it could be very useful to consider some types of sexual behavior as addictions.