Impeccable Reasoning

Being in the engineering industry for a few years now where problem-solving becomes a daily affair, my senior colleagues have all naturally developed a very keen sense of logic:

(While having lunch with colleagues)

Colleague: So, Ben.

Ben: Yeah?

Colleague: Why don't you smoke?

Ben: ... Well the right question is, why SHOULD I smoke?

(Pauses)

Colleague: To prevent SARS.

Ben: What?!

Colleague: When you smoke, you expose your body to a huge amount of toxins. Then after some time, your body will develop a natural immunity against the said toxins and even against some of the worse diseases.

Ben: Like SARS?

Colleague: Like SARS.

Ben: But... what if my body doesn't develop the natural immunity and I eventually die from the overload of toxins?!

Colleague: *Puffs a cloud of smoke* You sure you don't want a stick?

Ben: I'm good.