I was in this situation recently as I played Kings of War for the first time in a tournament. I got my ass kicked in all three of my games, but a little less each time.
I enjoyed myself thoroughly and I don't think any of my opponents are jerks for not going easy on me - it was all very pleasant, sportsmanlike and friendly.
I'd rather learn the game and I think I learn better from getting my ass kicked than having it easy.
With a kid I'd take a different tack, just because it's pretty common for younger players to be less cheerful about losing
Similarly, if my opponent looked completely miserable about getting beat I would maybe give some gentle advice in the least patronizing way I could. But for myself, in a tournament if I mess up, I expect to get trashed.