if not disrespectful (though he is the POTUS, guess he has the right to be a jerk), definitely unsportsmanlike and not very smart
If the GOP did this, you'd be declaring it a great political tactic.
upstaging someone is one thing, but pulling the microphone away from someone is totally different (unless there was a new crisis justifying it, but the unemployment problem has been going on since before Obama took office, there is no justification for this timing and only makes him look childish and adds to the perception of arrogance - "I am the POTUS! So go sit in the back of the bus.").
Does it actually work like that. My impression is that the President respectfully requests a joint session of the congress. Generally that request is granted, but it's not as though he orders anything.
I'll assume that the Speaker of the House will get on the phone to the white house and to the sponsors of the GOP debate and see if one of them is willing to reschedule.
Obviously, it reeks of an attempt by the White House staff to upstage the Republicans. You could spin it as a power play, but it just comes down to a simple gamble on the part of the white house that the Republicans (and their debate sponsors) would be willing to reschedule.
It could be in the best interest of the debate to go on after Obama's speech, as some questions could arise during the speech and it would be interesting to hear the candidates debate among themselves about who has better ideas than Obama.
And does anyone honestly expect any real substantive statements from either event?