Thats all they say to you, as in 'kick the person to prevent as much griefing etc'. Does not mean he wont get an account action aswell, as blizzard will never tell you what that person might get as punishment until its looked into. Its like when ive reported bots and the message is the generic 'thankyou for your report we will look into it' and said bot is still removed shortly after.
Also your issue could be put down to someone just not understanding whats going on etc. How stupid some players are is just astounding afterall (I have had 3 blood dps DK's in last 2 LFR's now, 15k-20k dps I even pointed out blood is only a tank spec now and my response was 'but I never die' FML)