If English is their first language, then yes, they speak English "perfectly" by definition.
Languages are a constant clash between its natural evolution and its rules (which came from past evolution)
If language hadn't evolved romance language speakers would be speaking Latin today, and English speakers would be speaking Anglo-Saxon maybe? (which themselves evolved from other languages)
Comments
If English is their first language, then yes, they speak English "perfectly" by definition.
Languages are a constant clash between its natural evolution and its rules (which came from past evolution)
If language hadn't evolved romance language speakers would be speaking Latin today, and English speakers would be speaking Anglo-Saxon maybe? (which themselves evolved from other languages)