The problem here is that 'cannot' can be interpretted in two different ways. To clarify, we may express these by decomposing the meaning of 'cannot' into 'are' and 'necessarily': 1a. If you are a bachelor, then necessarily you are not married. 1b. Necessarily, if you are a bachelor, then you are not married. When we initially admit that 1 is true, we are naturally being optimistic and interpretting it as 1b. But in order to apply Modus Tollens using 2, we would have to use 1a. The difference is that 1a implies that anyone who is a bachelor can never be married, while 1b allows for the possibility of a bachelor being married in the future. One must be very cautious of these multiple meanings when presenting arguments in the English language.