Facebook Fired me

Should what an employer finds on social media be grounds for firing an employee? Why or why not?

I think that if an employee breaks a policy that the company does like should be fired because I feel that if they would want to work there, they should follow directions. If people break the rules shame on them but dont post it. I say this because your embarrasing your company and yourself because this shows you are highly uncapable in having a job. I believe breaking rules for a friend is unacceptable and shouldn't give you a reason to do something like this.