What is the meaning of [He who saw what he likes shall hear what he does not like]

A man who claims that he always speaks his mind does not expect others to do
the same, and is annoyed when they give him a dose of his own medicine – that
is, treat him as he treats them. As was once remarked on this matter or free
speech: ‘You are forthright and outspoken. The other chap is just naturally
rude.’