You're comparing apples to hamburgers here. But first lets go with your scenarios. If a player did drop a couple of rounds bc of off field issues in college/high school, if they then played a couple of years on the level that their talent projected them they'd get a big contract and be treated like one of the best in the league (Randy Moss among others). If a player isn't drafted they'd still get to come to camp and make a team where their talent would determine their fate.
Now lets look at a better comparison... a player's been in the league for years when it comes out that he did these things in college and/or high school. He's already been drafted and paid. All that would happen is he'd be labeled as a bad guy. That's all that could happen. Jones violated the conduct policy that year... and then again when on probation. It's not the same situation. It's not like Pacman was keeping is nose clean and then some old dirt came out on him and bam, he's suspended.