Subject is usually speech, writing, art, or behaviour with a religious target — not a person directly. To describe the speaker, use 'a blasphemer' (noun) rather than 'a blasphemous person'.
常見錯誤
He is a blasphemous man.
His comments about the prophet were blasphemous.
describe the action or words, not the person.
The food was blasphemous.
The food was awful.
'blasphemous' is only about insulting religion, not about poor quality.