In essence, a business like ESPN (or any other business) has three considerations when something like this comes up:

1) Does the behavior affect the person's job performance?
2) Does the person's behavior affect his/her professional reputation or our reputation as a business?
3) Is anyone at the company uncomfortable working with that person because of their behavior?

Let's consider the two cases: first with Irvin.

1) Unless Irvin smokes on the job or smokes copious amounts it likely won't affect his performance that much.
2) Like I said earlier, pot is different than most drugs. Most people condone it's usage to a greater or lesser extent. If Irvin were an educator like myself it would likely be different, but I don't think people expect total sobreity from the anchors at NFL Countdown.
3) Unless someone is a complete religious prude then no.

Now HR.

1) Not really. Most of us didn't know this situation was going down until it happened.
2) To the outer public it won't have an affect until a woman comes forward, but HR's reputation within the office probably is mud (particularly among female employees).
3) I would think most women on the staff have a problem working with someone who repeatedly harasses women.
I'm down with OBP (yeah you know me).