Oh, Enjolras is pretty open with his feelings about people. It's just that personal dislike is very rarely a factor, even when vociferous and even violent disagreement is.

"He was a spy for the police at our barricade."

So, you know. That's what's between him and the Amis!

Enjolras is well aware of what Harry's reaction to a sneaking, deceitful spy is likely to be. But it's his own, as well; it's the general attitude towards spies in his day, even if Harry's temper will probably add some extra volume to the disgusted contempt.