Contrary to how you would have expected him to react, Wilhelm didn't react at all. No, he was too shocked to react. Here he was, being kissed by another man. Another good looking man, but a man nonetheless. Someone had just met, and more importantly than both of those things, a monarch.
And then, on top of it all, he propositions him for sex? Suddenly, Wilhelm felt like he understood what he had been missing their entire conversation. Now he was afraid of the details of what he had been missing. It all made sense. How had he not realized it before? The out of place English was obviously a code. An amateur mistake; it only made sense.
When he finally regained his composure, he shoved Eadric away from him.
"What do you think you're doing?!" He shouted, but of course, he had reverted back to German in all the confusion.