Mean messages

I had a user called Pulproman send me mean messages judging me. I don't even know who the person is and whoever it was came along judging me and hurt my feelings despite not even knowing me. Then whoever it was who goes by the name of Pulproman had the audacity to block me just because I told him or her that he or she is was wrong. How do I prevent people from messaging me in the future? I don't like people I don't know sending me nonsense messages especially messages like the user Pulproman sent.