Stress with an adult child

I recently learned that my older son 34 told one of his cousins that he was terrified of me during his childhood. I was shocked to hear this as I never used corporal punishment with him. I was very strict and spent a considerable amount of time working on his behavior because the first three preschools I tried did not appreciate his overly assertive, oppositional nature. I had him while I was in college and when I married, when my son was 2 years old, my then husband believed the only way to teach him to behave was to use corporal punishment. Eventually I convinced him to just not have anything to do with discipline and I would handle it, but this required me to spend a lot of time explaining what my son was doing that wasn't acceptable and how he needed to behave, as well as giving him time outs or natural consequences such as losing a toy. Somehow this has translated into his feeling that he was terrified of me during his childhood. I didn't scream, and certainly didn't hit him. I admit to being very strict but in order to get him to a point where kindergarten wouldn't be a series of phone calls home about his behavior, I really had to work hard to teach him how to behave in a socially acceptable way. The cousin he confided in shared this information with me, and now I would like you talk to my son about his perception of being terrified of me during his childhood. I never sense to that while he was young, but I've always admitted to being strict about how he needed to behave. I'm searching for a way to facilitate this conversation that will be productive and respectful. I'm saddened that my tactics caused him to feel terrified, but I'm also confused since I never sensed that in the past. I would appreciate any suggestions about facilitating this conversation.