Well, I´ve found an easier solution:
1. Whenever I feel the question is coming I strike first and introduce my car as my "midlife crisis mobile".
2. This takes people of balance, they usually give me a look and start thinking of a reply.
3. Before they say anything I ask "what do you prefer? a married mid life guy with a nice ride or a married mid life guy chasing tail or pretending to be a teenager?".
4. Since must of the time critics are soccer moms, they just stay quiet for a bit and then they have to admit the car is the best choice (if they answer).
5. Sometimes they try to strike back with the "not a family car" argument; my instant reply is: "well, that´s why my other car is an SUV
".
Sometimes I´m tempted to add the fact that my kid and my wife love to cruise in my car as much as I do, but why waste time on haters?