The discussion is essentially about whether you want to lull people into a false sense of security by encrypting some e-mails, or having people self-censor because they know that all e-mails are sent in the open. As it is, encrypting some of the correspondence will only deter those third parties who give up early. Meanwhile any larger organization, such as a state actor, will still be able to easily read your correspondence even with such an "encryption" scheme.