Drafting in a race is almost impossible to do - from a physics point of view. Everyone is over-analyzing that word right now in this thread.
The ladies probably meant "Stop running behind me, using me as a pacer or effort reliever" I get it, first half marathon and you wanted to run well - who wouldn't? Someone is running your pace, so why should you feel obligated to run in front of them or 30ft back? 98% of us on LR are "Hobby Joggers" or "Hobby Runners" or "Runners", so I can't automatically assume you were running this race to win and set an AR. That's why the concept of drafting is ridiculous in this context.
It is strange that a) you paced off of two women, and b) you were explicitly told by both to stop drafting.
I hope you ran well. Unless you are in a large group or duking it out for the win, don't just run directly behind someone...if you want to be "etiquette." When you are actually racing and the people around you want to beat you, by all means sit behind them and let them work. They will be pissed, but it's a race - not a fun run. The person leading you may get irritated that they can hear you breathing and foot steps falling all while struggling to run within their limits.
In your next race, try running BESIDE someone. Use your peripheral vision to gauge how fast you are running. That way, they can do the same thing and feel more comfortable seeing a partner/competitor rather than a parasite.