The church presents celibacy as a charism, a gift, given to certain members of the believing community as a witness oriented to the kingdom of God in which women and men will neither marry nor be given in marriage. 
The Sacrament of Orders celebrates and confirms the call of certain members of the community to celebrate the sacraments of the church with and for their sisters and brothers.
There is no logical or necessary connection between the two.  A person gifted with the charism of celibacy may or may not be called to Orders; a person called to Orders may or may not also be entrusted with the charism of celibacy.
The discipline that links the two -- that requires celibacy as a condition for orders -- artificially shrinks the pool of candidates for orders, and it disfigures the charism of celibacy. "Mandatory celibacy" is an oxymoron, if celibacy is understood as a charism.
Enforcing celibacy on a widowed deacon is simply, incredibly stupid. The bishop ought to be ashamed.