Punkawallah
Veteran
I think my English is no good and I've heard this expression before "on them". What does it mean by "it's on them" - what is on them?
Your English is very good. However, the language has been around for a while, and been moulded by its experiences and abused in its usage :-)
In this case, ‘it’s on them’ means -they- are the ones ‘doing wrong’, not you. The inference is that just because someone is ‘doing wrong/bad’, that does not mean you should stop ‘doing right/good’. Their actions lessen them, not you.
Hope this helps, feel free to come back if you have any questions. I like to get my ‘good deed for the day’ out of the way early. Then I can be a complete twat the rest of the day :-)