"Carlsen goes down further in my estimation each time I see him."
To be fair to the lad I've seen that happen 100's of times at blitz.
You move and within a nano second you know it's wrong.
You scream and a very natural reaction is to quickly undo the move you
just made. Of course you just laugh and resign.
Also in some places they play 'touch clock' the move is not completed at
blitz until till the clock is pressed.
V Radjabov the magnanimous Magnus walked into mate going for a mate.
MC (white to play)
MC played 1.Qa8 threatening the obvious. When 1.Bh8 sets Black problems.
Radjabov replied 1...Qc8+ and it's mate next move.
Here is a vid of the game. Watch the slap handshake Mc give Rad at the end.