Overreacting?

My husband and I just finished arguing over something and I'm wondering if I overreacted? My husband knows how I feel when it comes to doing things illegal like selling drugs. Too many people in my family went away to prison and have done stupid stuff because of drugs. I do not want that kind of life for me and my daughter and my husband knows this. So today I just heard him talking to someone about selling drugs. He knows I don't ever want him doing that because it's not worth the risk getting caught. After hearing it I asked him and he told me that he was helping someone sell some pills. I was livid! Like why would he do that? And what pissed me off even more is he is doing this in his job's parking lot!!!!!! Are you kidding me?? The fucking parking lot of your job??? Why would he be so stupid?? He hasn't even been at this job for a year yet! He was out of work for almost a year and now he finally has a good paying job and we just moved into a new home so I don't understand why he put all of this at risk! I told him that he was an idiot for doing this and I told him that if he got caught and lose his job or go to jail then I would leave! He has made so many stupid decisions that's caused so much stress on us that I'm done with it. We don't have a problem with money so I dont understand why he wants to do it, especially after he knows how I feel about it, and right in front of his job! Someone help me understand! He's gone now and now I'm wondering if I overreacted. Advice is much needed. Please help.