Umer Ibn Khattab made Mut'a haram from himself. Don't believe me, check these references from your so called SAHIH books.

Sahih Muslim Book 008, Number 3250

Sahih Muslim Book 008, Number 3248:

Sahih Muslim Book 008, Number 3249:

Sahih Bukhari Volume 6, Book 60, Number 43:

Insulting Mut'a is Insulting Sahaba because they practiced this during the life time of prophet Mohammad(pbuh) until Umer forbade it from himself.