I'm going to take a hard stand against letting my fiance's mother come to our wedding, regardless of anyone's opinion.
Why don't you want your fiance's mother at your wedding?
I just don't want her at the wedding, so please respect my decision.
That's a poor explanation. Don't you think this will affect your fiance, not inviting their mother?
I disagree. I have a right to invite anybody I want to my wedding. I'm the one paying for the wedding.
You're not getting married to yourself, so you have to pass these things by your partner first.