Logic error. You're saying that because one of the movement's founders believes something, the movement supports that.
The movement is for the dismantling of systemic racism, not the implementation of Marxism.
> You have stated that this is the group the Premier League supports.
Let's not introduce "group", but stick to "movement" and "organisation". "Group" might mean either of those things, so it's not helpful.
The Premier League supports the "movement". The Premier League is English and "defund the police" is a very American expression that doesn't cross the Atlantic well. The Ben&Jerry's cartoon probably explains it best:
https://www.benjerry.com/whats-new/2020/06/defund-the-police
In case the cartoon is insufficient, there's several hundred words below it to further explain.