This is the issue I have with these sort of brokers. I have been trading currencies for a couple of years now and they have also done this to me (ala FXCM). How many other traders have had their stop loss taken out and not complained.
Thought I would put my two cents worth. I trade with them and have found them ok. They charge no commissions but have wider spreads on stocks and futures eg. es has two tick spread and stocks have 5 cent spread. Margins are 3%. Hope this helps.