Wait a minute...

A guy opens up to you, is completely honest about avery sensitive subject and this is your reaction?
He trusts you enough to tell you before rather than after.
He probably knows full well that it might push you away but he feels that it's more important that he's honest with you.

As for the terrible Herpes!!

Jesus people, it's a simple fungal infection, it's just a cold sore on his knob!

Lets put this directly in perspective here.
If the guy came out and revealed that in the past he has had a cold sore on his lip would your reaction be the same?
If he did and he kissed you in the happy place you'd get genital herpes.