Quoting: Kalopsia
It's a lot more than two bad playoff games. That benching was a long time coming cause he'd been struggling defensively all season. I really hoped it was just lingering effects from the hamstring injury, but he had plenty of time off during the shutdown and supposedly got back to full health but still had the same problems in the playoffs. Trouba's value comes mostly from his play in his own zone, and I think the consensus is that he's pretty overpaid anyway, so he's a weird player to bring up.
Kempny should be traded because as you said, the Caps have a logjam on the left side. It sounds like the Caps want to bring Dillon back, so between him, Orlov, Fehervary, and Siegenthaler there's just no spot for Kempny, and his cap hit would be better spent on a 2RD.
Kempny was a lights-out penalty killer all year, and finished seventh among LHD in plus/minus. Trading Kempny because you think he's bad at defense, because sometimes guys get by him, is like trading Ovechkin because he missed a lot of shots.
Growing up, I thought Calle Johansson was bad at defense because I always noticed guys getting around him on odd-man rushes.
It was only years later that I wondered why he was always the one back to defend against the odd-man rushes, and I realized that actually Johansson was fine. Kevin Hatcher was out of position a lot, in order to get points, and Johansson was back to cover for him.
Do you think maybe that's what's happening with Carlson and Kempny, and that's why casual fans are scapegoating Kempny as being bad at defense?
I'm not opposed to trading Kempny, if Dillon wants his spot, or if Alexeyev is ready to play a top-four role, but the return starts with a 2nd round pick.