"You should treat other businesses with respect"
no business deserves respect. a business is not a person. a business does not have human rights, nor human needs. a business is a social construct, deserving of about as much respect as, say, the concept of a deity, or a work of fiction.
I'm not sure I follow your reasoning. Are you saying that suggesting a relevant and free alternative by a non-profit is disrespectful towards Dropbox, and should not be allowed?