I've only experienced the opposite. One time years ago I saw a woman punching another woman with a disposable camera. Security came out of NOWHERE and made her disappear. Anecdotal but I was amazed at the response time.
No response time at all in my case and I know CM's saw the entire thing.
Here is a true story that involved me, some people just should not and are not cut out to go to WDW.
I was in line, but already inside the tunnel area at the "tough to be a bug" attraction.
All of a sudden a guy next to me and I kid you not, he was a minimum of 6'8" or 6'9" and 300 lbs probably much more(basically one of the largest humans I ever saw other than NBA players in person). He was mumbling about the lines, he did not look happy and looked like he was in agony just being there with his family and mind you there were no wait times! That theater wasn't even 3/4 full after we got in.
Anyhow, he continues mumbling then directs his comments to me. I say hey whats up, he says if you touch my son again Ill destroy you, I will kill you. As he says this my hands were ON MY SONS SHOULDERS and had been for at least the last 3 or 4 minutes as we were waiting. Even as I replied my hands were still on my kids shoulders, I said what's going on I haven't done anything to you.
He says you touched my son, I was very polite and said that wasn't me, look my hands are on on my sons shoulders right now. He dismissed me and said do it again and I'll kill you. I was freaked out to say the least. So I look at another son of mine that was there and was standing next to the large mans son, I say did I touch you(talking directly to this kids son)? The son looked terrified so he would not answer. He didn't say yes or no, nothing. Right there and I don't care what anyone says I felt like this kid got beat at home he was afraid of his own father. He looked so scared at that moment my son's jaw was full open mouthing, .
This man's son who was probably no more than 14 was at least 6 foot himself and easily 200lbs and much larger than me, I weigh 142 lbs and hardly 5'8" so none of this made sense. Had I touched him everyone would of known, we were in single file in that exact area and my son directly ahead of me and why I had my hands on his shoulders, I tend to lose my balance. If I touched the kid he would of said yeah you touched me, he didn't. No one around us did a thing, but one guy says under his breath, your hands have been on your kids shoulder I have been here the entire time, but get the hell out of here.
I never touched his son and I don't believe anyone did, so I say hey I didn't touch your son, but apologize anyhow. I say if you felt I bumped him in line or anything like that I am so sorry. He again says touch my son again and I'll kill you. This guy for whatever reason just was not cut out for family time at an amusement park. The actual memory of this makes me feel a way, I fight it because what he did should not effect my enjoyment, but it's tough to forget. This guy could of killed anyone with one punch to the head.
After all this I thought I am not leaving this theater why should my kids have to leave(I had 5 in tow this time).. So I go in and watch the show and instead of just getting the hell out of there I waited outside because well I am not running(dumb). So the guy walks right by me with his family not making eye contact and that was that, never saw him again. I sure did monitor WDW to see if there were any issues that day though.
The CM's were girls, they were terrified and they didn't do anything and in this case. Looking back in hindsight I 100% agree. Escalation without security right there at that moment, well this guy could of been an issue. Had he approached me after I would have had to get security involved. Sometimes doing nothing is safest and in this case I think that was the right call. I don't think 6 security guys could of kept this guy down and it was only words, he never touched me. I was scared and as a male that's a tough thing to say, but I am not stupid.
The only other instances I ever saw was where once a mother acted unruly cutting in front of my wife and acting like it was my wife cutting. My wife and 6 of us for that trip were all together, this woman's family were at least 10 people behind us. My wife tried to explain to her if I cut then why are all 6 of my family together yet your family is way back there? This woman was a real piece of work. I had to beg my wife to walk away as she was taking the bait. Another time kids were swearing so I say please stop, one kid literally tells me to F off, then another person I do not know in the line tells his parents, "hey your kids are too loud and swearing", the parents(mother) says, "shut the F up my kids can do as they want". This was in the Peter Pan line, there were little kids all over. CM's simply ignored the entire thing.
So to me it is 100% the parents fault when this stuff happens, no one can convince me otherwise. Three instances in over 100 visits is not that bad I guess.