A statement widely used when someone does something morally questionable to get a step over another person. To a large extend I agree with the statement, if you are playing a game and you lose you shouldn't blame other people for winning or using the rules of the game in their favor.
We live in a world where rules really are mad to be broken, many laws and their subtext are cleverly worded so that people can work around them in many ways. This creates a gray area where people know of its existence but try to stay away due to controversy or not wanting to go against their personal moral compass.
As stated by the quote don't hate the player! Every body is a part of the game of life whether they want to be or not, and it is not an easy game at many times, I am a firm believer that anyone can get to the upper echelon of the game however the controversy comes into play when people get there using questionable methods.
Don't hate the player
Life is in many ways a hard, cruel game but it is also easy and kind in many ways as well, the game of life is one that has a basic outline and not much else, the players have to find their own way. With no clear story for any one person to follow it can be hard to know where to start and each new step to take, however on the other side because of this setup it allows for a lot of creativity in how you can get to the top.
By saying that life has a basic outline I mean that there are set rules around the majority of the world in the sense of laws however they can differ a lot from country to country and the different wordings can allow for different interpretations.
If a person takes advantage of the way the law is written and use that to break the law but get around the punishment, for example big companies dodging takes through having their HQ in a place with lower tax or just stalling court processes. If a person is running a company and they are able to dodge taxes through one of these loop holes you can't hate them for doing so, they used the rules in a way that is seen as immoral but it is not fundamental against the rules.
Hate the game
Now it is reasonable to dislike or even attempt to discredit people for using these loop holes however your hate would be misplaced on them. As the saying says hate the game, rather than solely hating the player for using what they could to their advantage hate the flaw in the system that allowed them to do what they did.
If you are to purely target the person who used the loop hole then even if you manage to stick something to them so they face the repercussion another person will just pop up using the same loop whole the first person did, which has been going on for centuries.
Instead target the flaw in the game/system, if you target the flaw itself and fix that, whether it be having the law completely changed or re-worded, you will see more significant change. Though because the game differs so much from country to country with the different laws it can be hard to see any real change worldwide as changing one law in one country can be good, it still leaves the entire rest of the world unchanged, which again is another reason to hate the game and not the player.