DP told me that he had herpes (facial - but extensive) when he realised we were getting serious. He told me what it meant, how he managed it, and how he got it. We've improved on that over time (he wasn't taking anything for the pain, and only took antivirals during an outbreak)
He certainly didn't minimise it. He takes antivirals continuously, and bumps up the dose if he's under stress, and so has a much reduced outbreak every 5-7 years, instead of the 2-3 year of painful outbreaks he had previously. If he's having an outbreak we're scrupulous about towels and bedding, and he covers it at night.
It's not shameful, but it is a communicable disease, with life-long affects and medication - it's not something to just brush off and dismiss.
15 year later, neither I, or our kids have been infected, because we know how to take precautions and we're realistic about it all.
What's unreasonable here isn't the disclosure, but his reaction to you.