Protect is related to Safe. Safe is related to Put. Put is related to Attack. 
Responsible is a synonym of Own. Own is a synonym of Acknowledge. Acknowledge is a synonym of Concede. Concede is the opposite of Protest. 
Protect <--RelatedTo--> Safe <--RelatedTo--> Put <--RelatedTo--> Attack 
Responsible <--Synonym--> Own <--Synonym--> Acknowledge <--Synonym--> Concede <--Antonym--> Protest 