"Technically, they are judges at court and should rule according to the law not their political leanings."If that were true you wouldn't have liberals appointing liberal judges and conservatives appointing conservatives, and fighting tooth and nail over it.
Also, the Supreme Court effectively makes the law, not just follows it, and that's true to some extent of lower courts as well, as most cases never make it to the SC.
It's not a coincidence that now that we have a conservative Supreme Court it's widely expected that Roe v Wade is going to get overturned soon. The law didn't change, but who's on the SC did.
"They should do their job irregardless of who is in power."
They have a lot leeway as to how to do their job, and many of them will use their power to pursue vendettas against people they don't like, as we saw with Abu Ghraib, Gitmo, Bagram, black sites around the world, and all the torture and murder that the police engage in.
Prison guards and employees of ICE and Homeland Security are also probably mostly Republicans, and it's hard to argue that their politics and world view doesn't affect the way they do their job or why they are in those jobs in the first place.