Is it legal for a state trooper to pull us over without any probable cause?

My boyfriend and I were on our way to a car meet today in Austin, Texas. We were cruising with a group of about 40-50 nice cars. We were all being respectful and going under the speed limit, minding our own business. All of a sudden we saw some of the people we were cruising with on the shoulder of the highway. We got a little further up and a state trooper was in the middle of the lane waving his hands for us to pull over. As we did, he yelled "Everyone get out of your cars and stand in the ditch". So we did. There were at least 4 state troopers. They slowly walked from car to car and checked license, registration, everything, looking for something to write a ticket for. I had sandals on and it was muddy, so I was actually standing on the shoulder but out of the way. One state trooper walked by me and hit his shoulder on mine and didn't say excuse me or sorry. ( FYI I am a woman ). They eventually wrote many tickets and let us go, there has to be something wrong with this. It was discrimination, and they were completely rude for no reason. Not to mention they had no probable cause to pull us over.