I think speaking up for your worst enemy shows an incredible amount of integrity and I hope that I would do so. I've spoken up for someone who I didn't particularly like (ok, not my worst enemy, I don't even know who that would be lol) and in doing so it knocked me out of that tournament. I find that to be a mark of integrity, not shame.
well, I wouldn't. Sorry if that makes me a "wrong" person in your eyes. And just because something is "right" doesn't mean we should always act on it. Have you never jaywalked in the middle of the night? Told a lie?
My mom is a therapist. Sometimes he needs to test people. One of the first 10 questions is: "If you could get into a concert for free, even though you had to pay and nobody would notice, would you do it?" If you say no, then there are two possibilities, either you are lying and the whole test is nullified or you have a more serious problem, which needs to be investigated further - not saying you're mental or anything, but that the answer is highly atypical if you're telling the truth.
As for the extreme example scenario, if we leave everything up to social norms, culture, and whatnot, then what if 1 particular culture, let's call it Culture Y, thinks murder, rape, and child molestation are all "right." Does the fact that it being normal in Culture Y make it right?
I'm not proclaiming to know the answers here. I just hope that we as humans have the ability to use reason and logic to determine right & wrong as opposed to opinions, cultural norms, etc. I feel like accepting something as "right" just because everyone around you is doing it is the same reason slaves exist, Jews were/are persecuted, gays are vilified, etc. At what point do we stop hiding behind gray areas and decide "no, ya know what, murder is not cool."
bring out the big guns, huh?
Most of the examples are way too extreme for the situation you are talking about, like how could I stand for murder and genocide?!?!?!
I think for the most part humanity shuns people that kill other people, because, you know, they are impeding the species overall. However, we don't shun killing a known killer often (death penalty), even though it is a killing just the same.
Americans think they were on the "right" side of WWII, yet they murdered hundreds of thousands of civilians in the bombings of Hiroshima and Nagasaki all in the sake of ending the war?
Would you kill a person to save 100? (e.g. the famous train experiment).
Did you think the murder of Osama bin Laden was: "you know what, not cool"? (?"I'm just glad Obama didn't present the 'There's an unstoppable asteroid heading our way' speech." - huh?)
I mean, I seriously don't want to play devil's advocate for people doing genocide, slavery or child molestation, like way to take what I said out of context. Again, I think the world is shades of grey, but child molestation is just a teint of very very very very very very very very very very dark grey - nah, black. 
I will admit my ignorance though when it comes to a lot of other cultures. The fact that certain Asian cultures value someone exploiting a system, even when it means doing harm to others, makes me question their entire belief system. How can one value doing harm to others?
I mean harm as in the other person might not enter the train/movie theater, might not get as much food etc. Not as in you're gonna get hurt!
I think the key question in all of this is exactly what you posed. How do we determine right and wrong? The golden rule is a great starting point imo.
I think this is fair for the most part. I try to live by that, too. Perhaps I fail sometimes or other people fail my expectations, but yeah, its a good starting point.
Since I expect nobody to speak up for me at the poker table, except for relatives and very good friends (like at a homegame), I guess it's ok for me not to speak up, if I feel like it
I did not quote the rest of your stuff, because I am not in the mood of going into child molestation, it sounds too much of "think of the children" type of argument.