<human>: Back story: My sister has had a habit of dating the 'wrong' type of guy.  Her present wrong type has recently been caught installing an app on her phone that forwards all of her PM's to his account.  She'd kicked him out over it, filed charges against him, put a restraining order on him and then a couple of months later drops all charges and takes him back into her life.  She has two children who can't stand him. Her best friend won't visit while he's there.  My mom can't stand him but is still going to Xmas dinner at her house which he'll also be attending.  

Personally, I'm worried that I won't be able to be civil to him and would rather not ruin the event so I've decided to just not show up, send presents over with my mom and hope they have a great time.  Problem is that my sister is now furious with me and told my mom that I ruined Xmas for her.  As sis put it to my mom, she doesn't understand why I won't respect her choice.  Well, it was a stupid choice, imo.  I'm not going to sit there and pretend that I'm having a good, familial time when just looking at the goof upsets me to the point of reacting.  He's like the red-headed bully in A Christmas Story to me: a veritable fist magnet.  My hope is that she eventually sees that my obstinance is for the better good of the season but given her temper and surprising talent for holding onto grudges, that is not likely to occur any time soon. Le *sigh

Provide a brief overview of the text.
<bot>: Sis's boyfriend is an a-hole so I won't go to her house for Xmas dinner.  Now I'm the a-hole.