Fired because of a race, sex, or being sick - you have a cause.
Fired because you chose not to come in, not giving any notice, not calling in, just choosing to not come in, and hurting the other 50 employees at that restaurant, not cool.
Not coming in to be part of a team when a boss/owner helped you out when times were tough in the past is just hurting the people, not a cause.
Also, was this a 'Day Without Immigrants' or a 'Day Without Illegal Immigrants'.