Well, it's hard. Defensive driving often means that you have to pick lines that makes you slower (but that blocks the sweet spots for the driver behind). Just being faster than the person in front of you doesn't in itself make you entitled to a free pass (unless you are on different laps). What I find is that a lot of people online are very impatient. They expect to overtake at the same time as they catch up with another car. That is not how it works in real racing, the faster car will just have to wait for a good opportunity before they can overtake. And the ring is a long track, opportunities will come, and there's actually quite a few good places, even though the track might be a bit narrow in between.
Driving on the grass in order to overtake is not something I like, but it should mean a warning, not a kick.
While I agree with the concept, the problem is that a lot of races online feature a large number of cars and a relatively low number of laps... in real races you are looking at at least 20 laps on any normal sized track and even on the ring I doubt you would have less than 5 laps.
With only 1 lap of the ring or 3-5 laps of something like Laguna Seca you dramatically reduce the number of passing opportunities and if you have 9 cars ahead of you and are shooting for first, you may not actually have 9 clear passing opportunities before the race is over.
That said I think a lot of people need to realize that that what you see happening (even as host) isn't necessarily what really happened... a lot of time lag causes things to look one way to one person and differently to another often causing things to happen that a person just can't control.
For instance quite a few times I have done NASCAR on Daytona and we are all holding tight around a corner 3 or even 4 wide and then something happens... I know I was holding dead solid with my wheel, I have watched the line and I was driving perfectly... then there is a spinout and someone is blaming me for smashing into them or driving dirty...
I know for a fact I didn't, but that's what they saw on their screen.
Then there is a weird little dip right after the start line on Daytona that causes your cars suspension to go all weird sometimes... I have been pinned in next to the wall going into that spot sometimes and I have no choice but to hit it, and when I do my car wobbles often making contact with another car and then I get blamed for ramming... well sorry but it's not possible not to in that spot and you pinned me into that location.
Also sometimes you come up on someone and are going to collide and the game ghosts them to prevent it... but then sometimes you barely touch them and the game glitches and they get flung as if they were shot from a canon.
The problem is hosts seem to always beleive what they experience was a: intentional and b: preventable.
Truthfully it's often just not... so kicking people for weird occurances ultimately means people can't race close or they risk a kick.