It is not inherently disrespectful, but within the culture of sports, it is seen as incredibly disrespectful. I personally view it as hilarious but your view -- my view -- as people not living within that culture doesn't really matter.

This is akin to saying people in burkas look weird. Well yes, because I don't wear a burka, and none of my friends or family wear burkas. But if you go to a Muslim nation that requires them, the women without the burkas are the ones that stand out.

The culture of sport has many unspoken agreements that tend to be adhered to, and not running up the score (except for in college football) is one of them. There is a silent agreement between both teams to not run up the score before the game even starts, to ensure neither side has to suffer the embarrassment.

So when someone breaks that silent pact, it sticks out like a sore thumb and you begin to question the motives of the coach calls the play, or in other cases the Quarterback who audibles out of a play to run the score up. Coaches are usually settling some grudge, and Quarterbacks are usually riding their egos into the sunset.

Either way, it's a really dumb thing to do because football is very much a sport of momentum because of the sheer number of personalities on both teams that you have to manage each game. Running up the score can cause a split in the locker room and demoralize your own team, or paint a huge target on someone's back that's on your own team. All of the players in the league belong to the same club and they all know what the silent agreements are. In the next game, some other players on the opposing team might use this slight to pump themselves up more.

In general, you don't really want to make waves in the NFL. Don't know why the Chiefs decided to run this trick play at the end of the regular season while they were up big instead of saving it for the playoffs, but it will probably come back to bite them in some way or another.