Newbie ? - what is the dressage whip for in lower level?

You don't hit people in competition.

You surely don't hit people in competition, but collecting rings and warm up rings are often war zones!

I've been hit intentionally with a competitors whip previously - I beat her top student at the state championships on the first day of competition, on a mare. The next day of competition, I was out warming up next to my arena about to go in, and this woman (who is a very big name here unfortunately, mainly due to her $$'s thus ability to import every horse she rides) comes straight over on her stallion, knowing full well my mare was well and truly in season, side swiped me so her boot hooked on mine, then gave my mare a good whack on the backside. Mare obviously freaked out. I went straight into the arena, and said competitor continued to circle at A for my entire test. As soon as I finished the test, she moved on.

My coach was about ready to explode I think!!

Are you serious/??? I am incredulous. People actually hit each other or each other's horses in the warm up arena? I have never heard of such behaviour. I am flabberghasted. I can only imagine hitting another person's horse if it was absolute self defense.

Oh yes Tiny, it can be a pretty nasty world out there. I do try to keep right away from the main warmup and find a corner somewhere, but the grounds where this championship was being held, are very short on space so there was no avoiding riders.

We have a few down here that think they are so high and mighty, and will just ride their lines without even taking notice of other riders. I'll be warming up a young horse that is obviously very tense and will be doing some lateral work - which takes priority in a warmup, and have these riders coming straight for you. You either need to jam the breaks on, or rip your horses head off to get out of the way!!!!!

Or like two top international riders that hated each other coming at each other in extended trot through the diagonal and meeting in the middle because neither would give ground.

Poor horses.

I need my whips to defend my space. They stick out like fenders and it will be the other person that ''runs into them'' not me hitting anyone.

WOW is all I going to say! That sounds really nasty. I haven't been to many shows but I have to admit people were very nice at every single one I went to (including big MD-wide one). Also people were quite considerate in warm-up ring when it came to space and practicing path (this includes very big eventing event I helped at, the warm up was right next to us).

P.S. Although I have to say my mare wouldn't let someone to get close enough to get me with the whip...

You should try the mini horse world, I read last year about one competitor deliberately driving into another in a driving class, the innocent party ended up with a broken leg

Hmmm...and I hope the offending owner ended up with a broken face!

Do they even get penalized or event disqualified for that? I'd expect it to be on way.