Attendance at a wedding should not just mean you want to go to a nice party. If I accept a wedding invitation, that means that I am endorsing and celebrating the marriage. There are many “weddings” I cannot celebrate for various reasons, so I do not accept those invitations. This would be one of them. Don’t go in for the online drama, just don’t go at all.
Just don’t go at all...
That goes double for the groom.