You always have the right not to answer. I'm not sure why someone would think they have the right to individual communication, material information is released to all shareholders, and management is entrusted by the shareholders in the meanwhile to manage the company.

Of course, IMO, it's always better to talk to your shareholders...but if you're busy, meetings, business, etc. and nothing material has been released that is of an urgent nature, then a CEO might prioritize the time of the discussion when he can better focus on it, nothing wrong with that IMO either.