Someone said that gullible people are born continuously — and every con artist knows this.
Literal
Being-deceived-easy person [topic-は] constantly being-born [quotative-と] said person [subject-が] exist-[but-が], fraudster [topic-は] all of them, this thing [object-を] know-[state-ている].
A wry observation in formal literary style. 騙される ('to be deceived') + ~やすい ('easy to X') → 'easy to be deceived, gullible'. 詐欺師 ('fraudster, con artist') is the formal word for someone who commits 詐欺 (fraud). 承知する ('to know, understand, acknowledge') is a formal verb. The phrase alludes to P.T. Barnum's 'A sucker is born every minute'.