When it’s a presidential address to the nation, broadcast networks should interrupt entertainment, period. Now you can quibble with the president as to the wisdom or timing of an address to the nation. Beyond that, I’d say, if you don’t want to hear the address, then find something else to do for an hour.
I kind of like that he scheduled it for prime time. That way the networks right (mostly) right back to regular programming (at least NBC did), and we didn’t have an hour of the talking heads talking about what the President talked about.
Also, I don’t know that Obama scheduled it. I’m going to guess that he mostly went with when the service was scheduled for - they might have jiggered things a bit when he asked to speak, but I’m going to say that the service was going to be Sunday night regardless.