Because when I see players like ARod or Cruz helping their team win, it makes me sick to my stomach. All I think is what a freaking cheater.
I am not naive enough to think that all Red Sox players were always clean. As much as I loved Manny when he was here, I would not want him back on my team now, knowing what I know.
IMO, the Ortiz case is different, for many reasons that have already been stated. If he failed a drug test today, I would have a difficult time rooting for him, even with his great legacy.