Today, I announced to my friends that my grandmother is dying. My best friend pulled out his phone and casually announced, "Technically, everyone is dying." FML
For the next few days every time he comes to you with something important... just pull out your phone and casually respond with "technically,______." Sorry about your grandmother OP.
Many people can't deal with serious situations in a subtle manner. No need to ditch them as a friend just because they can't handle a tense conversation.
They should not be considered your best friend. A best friend is someone who actually cares, or in my case was more like a sister than a friend. I would be careful around this one if I were you.