It's a good point, and its an admirable quality, but people who do habitually throw litter around and demonstrate other antisocial behaviour tend to be a little troubled, psychotic ,densitized to the needs of others and the planet and lack the caring gene so I think its a good reason to be wary of them. I think its also a mistake to think you are going to educate them into better habits unless they are young children who dont know any better and could benefit from a bit of advice. They know too well they are doing wrong but dont give a toss, something else they want you to know. People also have mobile devices so they can photograph you , record you, and also call their mates to come and get you quite quickly so the speed of technological development means that things can turn nasty very quickly.

The other side to that coin is that you can also use that technology to do the naming and shaming without having to put your life on the line. Think of those people caught on youtube showing racist and abusive behaviour. They were recorded and caught that way. There was another man on youtube caught beating up his dog and the same happened when it was filmed by the next door neighbour and got a record number of viewings and appeared on national TV. Perhaps the way is to keep quiet, keep yourself out of danger, but keep a record, and if possible, pursue them by different means rather than direct confrontation.

I used to feel the same as you and did the same as you. Once I said something to a woman at a bus stop for being obstructive to others trying to get past her - she called her bloke who then turned up in his car and threatened me. In another incident my partner scowled at a speeding driver when he was trying to cross the road; the driver reversed back about 40m, pulled up and tried to attack him. It only stopped when I pretended I was calling the police on what was a hairbrush but he could have beaten him to a pulp. Another incident was when I tackled a group of teenagers from preventing my children using the slide in the Horniman Triangle- they were just sitting all over it blocking off my childs access. They turned nasty and one of them went across the road where they lived to get their parents. I called the police who turned up too late after we had left in a lot of fear I had to say as it was difficult being in that situation with young children. Finally a colleague who was out walking in a country lane shouted at a speeding driver who then drove back and ran him over. He spent weeks in intensive care. When he came out he was too emotionally fragile so had to take early medical retirement.
When I had my old car stolen twice in as many months, and apparently by the same people on the Honor Oak Estate who seemingly used it as a taxi when they were stuck, the police said I had the right to pursue costs but they were clear that I should not as the people in question were known for violent retribution and I shouldnt do so. At the time I was so outraged that I was keen to pursue 'justice' but it would have come at a price which I decided I wasnt going to pay.

There also have been 'famous' incidents over the years; the one in Holloway Road where a bloke was killed for telling someone off for throwing chips at his girlfriend on a bus,
the have a go hero in Swiss Cottage who tackled some bank robbers, the one where a man ran out to stop people taking his car and they ran him over and killed him. In the last few days someone was nearly killed for asking if a crying baby was ok. In Manor Mount a man was beaten up for remonstrating against drivers driving down the wrong way.

Taking action against misdemeanours is 'just' but can lead to unimaginable consequences. Having a hero inscription on your tombstone isn't a price worth paying.