As mentioned before, the Doc situation was very different. For one thing he was the manager at the time. It also involved an employee and could easily be construed as detrimental in a purely professional sense. Lastly and most importantly, it happened a long time ago in a, say, moral climate that was very different.
As for Giggs - yes, it's not unreasonable to claim that what he did suggests something about what kind of man he is: Of course it does. But without knowing the full story it's far too armchair-y to simply conclude that he's a despicable human being. Perhaps this affair is the biggest regret of his life. What if this is the case? Doesn't excuse what he did, but paints him in a less hideous light? Where do you draw the line with a thing like this? Does cheating on your wife make you unsuited for the manager's job? No? But doing so with your brother's wife does? But, again, what if Giggs is genuinely heartbroken and repentant over this? Do we ask him to take a lie detector test before offering him the job?
Absurd, of course. You can't hold a prospective manager to moral standards which aren't relevant to the actual job, it makes very little sense. If his transgression had been of a nature which would likely damage United's reputation, the matter would've been clear. But this isn't the case. Everyone knows what he did, it's water under the bridge at this point.
On a more sinister note, one could also add that being an utter arsehole does not necessarily make you a bad football manager. Some would even say that the very opposite is true.
Standard caveat: No, I don't want him as our manager.
