Was I out of line for exposing my cousin as a liar?

My cousin said he managed 300 high net worth clients as an investment relations partner and I told my parents I thought it was a lie cause nobody has time to manage 300 high net worth clients and he doesn't even have a graduate school degree, did not get straight As in undergrad, does not have a CFA license or any license at all, got laid off from his last lower level job due to poor work performance, and nobody has time to manage 300 people in a deep and personal way. Now he isn't inviting us for walks at the lake anymore cause I accused him of lying about his credentials. It's sad when a family member ignores you, but on the other hand, it was either believe his lie or not believe and have him avoid you.

Was I out of line for exposing my cousin as a liar?
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