Not sure why Joker is seen as the bad guy

Rating: 10/10 (19 November 2019)

An awesome movie, just not sure why people refer to Joker as the bad guy or villain.
All I could see was a guy struggling with a world/life that was treating him pretty cold, and he took a position that it was time to stand up for himself.
It tells a story about hardship, and how a person could deal with that hardship, you either take a stand or do what the man tells you to do. Sort of a bit like Hong Kong at the moment, people don't take what the man (Lam) is telling them to do, they decide whether they will accept it or not, they respond accordingly.
The movie portrays Joker as a very strong character, despite disadvantages he is able to do what he thinks is right. Not your classic good guy vs bad guy, in this movie maybe the person they call villain is actually a good guy?