Can someone do bad things and yet still be a nice person?

There's lots of gray areas. The true sociopath, the one with no conscience, I would consider "bad." It's estimated they make up 4% of the population. Those who also recognize they're harming others and continue to do so, both mindfully and of their own volition, I would also consider "bad." 

Of the person who abuses his or her kids, also bad. Of the person who watches it... that depends. You're as much of a psychology nut as me. So, you know about things like the Milgram experiment (shocking the person on the other side of the wall at the urging of authority). There are lots more, all suggesting we're prone to do as we're told. When you throw in things like Stockholm Syndrome and PTSD... we know that people also do what they have to do to survive and keep their mind as intact as possible under the harshest of circumstances. Well, that would make the inactive viewer "normal." Sadly, it makes them remarkably normal. And, we see this in all kinds of circumstances too. For example, the bystander effect. If there's a group of people, there's a good chance nobody will step in to help a victim. 

So, I can look at these situations and say they're certainly not nice, but are the people really bad? Bad for doing what their brains are expected to do? My mom watched all her children get beaten. To this day, she believes we deserved it, though perhaps not so hard. She never understood what that meant to us. She never understood what it was like to grow up in a household where our only daily motivation was to find a way to not get hit. Now, she's had a stroke and pieces of her brain are missing, but that's the way she felt when she was "intact." She was always broken. I don't think she was a "bad person," but she was a bad mother and a very damaged person.  

As I write this, I can think of so many examples where people have done horrible things or failed to act and I personally cannot fault them because I know it's part of the human condition. And, that is precisely what makes people so dangerous. Because they can and will do unspeakable things or fail to act in order to cope or because they don't feel personal responsibility. It's enough to make me want to swear off people altogether. We cannot hope for more. Nice people and good people do bad things. 

But, at the same time, we have people who break from the norm and do extraordinary things. In the US, we hail the passengers of Flight 93 on 9/11 as heroes. And, they are. If they were exhibiting "normal" behavior, they would have sat idly by during the hijacking. They didn't, and that's what makes them so special. That's why we honor them. First responders of all types and the military sit in the same realm. They go into danger time and time again. They're not normal. Thank goodness they're not. Teachers who have protected their students in school shootings and died as a result. Not normal. This is why we celebrate their lives. I could go on and on, but the point is, we have a lot of respect for people who ascend; for those who do great things and sacrifice themselves for the good of others. That's purely because it's not normal human behavior to do so. 

Yet, I also have a feeling that our heroes are remarkably human too. And, I'm sure people in all those groups I mentioned have done bad things. We wouldn't call them bad people, not by any stretch of the word.