An alternate interpretation is that the OP doesn't want Monsanto to grow their food because of their involvement in the military-industrial complex and poisoning of the environment, not because their defoliant was contaminated.
But if you do and his head starts to hurt so he grabs some Aspirin, don't ever bring up Bayer. ;).
If the shareholders are lax in demanding moral behavior, then immoral behavior will result. The company should absolutely be shut down.
> Otherwise, they'll just join other companies or start new ones and continue to do evil
Actually, nobody will want to hire them. After all, nobody wants to lose their money in a company that was shut down.