Would you judge him if he left?

A married couple has a 5 year old son. The husband notices as years go by the boy looks nothing like him. He questions his wife and she’s furious he has doubts after all this time. Husband goes to Walgreens and gets an at home dna test and secretly swab himself and the son without the wife’s knowledge. Days go by and the results are in and he’s not the father. Now this man is the only man the child knows. He’s filing for divorce and want nothing to do with the wife because she lied and basically stole his “son” from him. Would he be wrong to want nothing to do with the child because he’s so hurt, or should he stick around being as though that’s all he knows?