IndyCar Racecraft Question

I'm ran the 8:00 ET IndyCar race at Sebring last night. Not bottom split but towards the bottom.

I'll preface this by saying that I don't run a lot of IndyCar especially on road courses but I am pretty familiar with Sebring through GT3 and feel fairly competent on the track. I practiced about 45-60 minutes before the race and and wasn't running great times but was gradually getting faster each lap.

I qualified towards the back. May P22 of 27. Race starts and I'm just running. No incidents outside of a couple of 1x's. I work my way up to P14 by about lap 30. P1 had just passed me to put me 2 laps down. P2 is approaching me as I get onto the Ullman Straight. He gets a good run off of T-16 and is about .5 seconds behind me at we approach T-17.

I know through multi-class racing that if a faster car is approaching, I should hold my line, not make any sudden moves and it's the faster cars job to pass me safely. In this case, I was absolutely in the racing line, I see P2 approaching and held my line. But I also slowed down a bit entering T-17. I didn't brake but definitely let off the gas a touch because I didn't want to overshoot the turn and cause problems for P2 thinking he would simply pass me in the turn.

Well, he didn't. I kept his foot in the gas and plowed right into the back of me, ending his race and mine. Then he started flipping out on the radio telling me I brake checked him and why didn't I get out of the racing line or tell him over the radio that I was slowing down going into the turn.

I jumped out of the lobby. I didn't know what to say. I didn't feel like I did anything wrong, per se, but maybe there's a different protocol in IndyRacing on that type of situation.

So my question: What obligation do I have as a slower driver to a faster driver in an IndyCar race

And if that guy happens to be reading this, I do apologize for wrecking your race.