I don't understand. How does a bit of turbo lag make your vehicle unsafe? All turbocharged vehicles have turbo lag to various degrees -- it comes with the territory. If you feel that the vehicle is unsafe because of turbo lag, it is something you should have noticed when you test drove the CX7 you purchased.
However, if you feel that there is something wrong with your particular CX7, then take it to another dealer to have it looked at if the dealer you purchased from is unable to fix the problem. You have a warranty for 4 years / 50,000 miles; I would suggest using it. If Mazda cannot fix the vehicle after multiple attempts, the next step would be to become familiar with your particular state's lemon law.