I think for the argument to work as it being "worse", it would have to minimize the modern version of racism completely, which isn't how reality is.
Racism wasn't systematic, it is systematic. It wasn't more common back then, it's still common. To say murder based off of racism "rarely happens" isn't really true, it's just not to the degree it used to be. But it doesn't mean it rarely happens, it means it's less likely to happen than it used to be.
With that being said, you can talk about heightism and how it effects millions of people (especially men) without comparing it to another social issue. They're just so completely different issues that it's almost comical to compare the two.