DUI is a bad one. However, I know several otherwise good people who have a DUI on their record. For me, what they do after the DUI is the indicator of if they deserve to have respect restored. Did they take the infraction seriously and own the mistake? Did they take measures to ensure that they would not get another DUI? If necessary did they enter into counseling for substance abuse?
I don't think this makes Mark a bad guy in and of itself. The proof, either way, is how he handles the aftermath.