As a meeting invitee I want to be able to still see meetings that I have declined in my calendar so that I'm still informed on what's going on and I can easily re-accept the meeting if my plans change.
I wouldn't want to see all declined meetings all the time, though, because it would be distracting. I would prefer a toggle either in Calendar Settings or in the Calendar View itself to show or hide declined meetings. Declined meetings could then be displayed using e.g. a strike-through font.