It's not political interference, but rather the firewall that provides judicial independence in the US system of government.
The system of checks and balances prevents the legislative branch from imposing on the judicial branch like that.
IF the legislative branch thinks a justice is misbehaving, they should impeach them. Otherwise, that's that, and there's nothing left for them to do.
Yes, Republicans don't believe Thomas should be impeached. Well, that's that. Without widespread consensus that he should be impeached, that's really the end of the issue.