If you consider any shooting game to be defensive training, then yeah, it can get you killed. Shooting games like IDPA usually involve trying to get the highest score in the shortest time while following a known COF where the shooter is already told exactly what is needed to get through the stage. There are no penalties against tactically unsound practices so long as the requirements of the COF are met. For example, there is no penalty for exposing far too much of yourself to the opposition who may then have the opportunity to easily shoot you.
To be successful in such games, shooters optimize time and accuracy and in order to score, shooters must shoot. These and given that shooters already know the COF and exactly what it takes to complete it teach absolutely nothing about some of the most critical aspects of gun fighting, threat identification and shoot/no shoot decision making. The shooter goes in already knowing they must shoot.
Also, games like IDPA have a linear orientation to gun fights. Threats are engaged sequentially and there is absolutely no concern that downed threats you think are out of the battle shooting you or getting flanked by threats that you didn't even know were part of the situation.
The COF is known. The threats are known. What is needed to defeat the threats is known. The shooter in IDPA already has a whole bunch of the critical information determined in advance such that he isn't having to make a lot of critical decisions about which the wrong decision could be fatal.
Games like IDPA simply do not offer the kinds of simulated fight experience present in the real world or in FOF training.
There is no doubt that IDPA and other games can help with shooting skills, but it is naive to think that IDPA is teaching you or providing you with gunfight/battle training.
"If you look through your scope and see your shoe, aim higher."
-- said to me by my 11 year old daughter before going out for hogs 8/13/2011