That is, by definition, a racist sentiment. I know that you won't see it that way, but it's still worth pointing out anyway.
What a person does or does not take offense to is entirely up to them. I happen to think that it's reasonable to consider both the context and the intent of what's said, but some folks just like to get wound up about things.
There are lots and lots of people alive in their 40s and 50s who survived or had family lynched. There are lots of people in their 20s and 30s who's childhood (like what side of town they could go to and what girls or boys they could date) was deeply affected by aftershocks from this.
It's not so much about taking offensive as not triggering something that is still salient in a lot of people we should want to feel comfortable here.
That's a lot of fucking context.
Remember, lynching was a mechanism of control to keep minorities well behaved. The senate only apologized for lynching in the US in 2005 (too many republicans objected before that). There was a lynching in 1998, not to mention several more recent gay bashings that meet the criteria of lynching. It still happens. The relevant context isn't mine or yours, it's the minorities. Take a damn sensitivity class. This is controversial?
There is no context where a community of white people casually joking about lynching isn't going to cause minorities to feel subliminal racism. It's way different then casually saying you baked a pizza to a jewish person.