Yeah, he merely quoted a diss track that famously escalated a previous grudge to murder. Who could ascribe anything but jovial intent to that? Why should somebody as famous as Gary Tan expect to have unhinged followers who could be inspired to act?
Seems like he was hoping to get his twitter followers to harass them in a manner similar to the way he did -- otherwise why tweet it?
Probably receiving death threats causes a lot of real anxiety (not just the PC snowflake kind). That's a lot better than an actual assassination, but it's not nothing either.