Don't jump to conclusions about what this man did or didn't do. Here's what happened to someone I once met:
He had been viewing legitimate porn (!) and hanging round some dubious chatroom. Somone on that forum sent him a file and said, "I think you'll like this!" He moved the file to a memory stick (I think he was at work, but this was his big mistake) and then had a look. When he clicked in the images some were of underage/children. He was shocked, closed it down and deleted the file. Then a colleague, looking for a lost file, searched in the Deleted box, found the images and reported him.
Now that's his story; it's not very wholeseome, and I don't know if there is any more to it than that. But this man was taken to court. He was found guilty of possessing indecent images, but at the the very lowest level, and given a long period of probation with psychiatric reports etc. The police and probation service concluded that he had no interest in child images and the chance of his reoffending was minimal.
However, he lost his job, his marriage, and all contact with his children. He received death threats. He suffered with mental health problems. He left the area, and got another job, and years later he ended up changing his name because it's all out there if anyone googles his name, even though his conviction is now spent. He is, however, on the sex offenders' register for life.
I also heard of another man - a vicar! - to whom something similar happened.
So don't conclude that this man is a monster. Many men view porn, and it is easy, particularly for somone who's a bit clumsy with technology, to find themselves almost accidentally becoming a sex offender. That doesn't excuse their grubby behaviour and sleazy habits, but images are passed around so casually that they may end up on the computer of someone who never wanted them. Some of the "perpetrators" of these crimes are also victims of others trying to sell their vile materials.
I think you should put this behind you and stop feeling tainted by association with this man. You don't know the details or the circumstances, and you can't do anything about it anyway. When you knew him, you both lived in more innocent times, and maybe you can even feel some compassion for him now that he has ended up in this pitiable situation and will be disgraced for life.