The arithmetic is not that clear cut. Especially for Labour MPs whose support is predominantly remain. If Brexit goes tits up, the current crop of MPs will be toast if they voted for it. We have a representative democracy where MPs are supposed to represent the best interests of their constituents, not necessarily their views. Take Capital Punishment as the hackneyed example.
Of course - neither path is clear cut as we are in uncharted territory and it comes down to a matter of political judgement.
Having said that I think the evidence shows that Corbyn has made the right choice here for four main reasons:
1. the country has never given a mandate to join a european super state
2. the majority of voters and the large majority of constituencies voted Leave (therefore the constituents are being represented)
3. the data from the Guardian survey posted above shows that this is the correct strategy for retaining the widest (if not the deepest support) and
4. the EU itself is heading for a clash between its political and economic goals as we have sen in Greece and therefore it is likely that other countries will follow us out.
Nobody will know if we have made the correct decision or nor for years - perhaps centuries.