Sorry I wasn't clear. When I said "most of the kick shots I've seen in league play are just an attempt to hit a ball so your opponent doesn't get ball in hand, so those should be marked as defense", I meant that those particular kick shots should be marked as defense, not all kick shots.
If they make a ball attempting to play defense in any situation, you don't mark it as defense, so the intent doesn't matter in that scenario. It's deciding whether a kick is an honest/realistic attempt to make a ball that can be tough to call. My contention is that most kick attempts at a ball that isn't hanging in a pocket are more about making a good hit, thereby defending against giving up BIH, than they are about making the ball. That's usually true even at a higher skill levels; the difference is the degree of cue ball control.
At higher levels of play, you might be able to discern the intent of the shot by the speed in a lot of cases, but for lower skill levels, the speed usually has more to do with their lack of control or preferred kicking speed that it does with whether they are truly making an attempt to pocket a ball.
In any case, I'm not implying that it's illegal to consider wild kick shots offense; I'm just saying that my bar for an offensive shot is considerably higher than "it might go in somewhere".