How do I remove (un-apply) a named filter from a Procurve switch port using the CLI?

I'm an old ASE and haven't done anything Procurve or switch related since nearly 8 years and starting to forget everything, so bear with me if I'm talking nonsense.

That filter list tells me that you should remove the ports from the filters, not the other way.

Old question, but looks like you never found the answer. I had an old filter config from before I created some trunks. The filter rules contained ports that were now in the trunk groups, and this was causing trouble for the switch.

Switch51(config)# show config

; J9773A Configuration Editor; Created on release #YA.15.12.0007
hostname "Switch51"
trunk 23-24 trk1 lacp
filter source-port "21" drop 1-23
filter source-port "22" drop 1-23
Switch51(config)# no filter source-port 21-22
Invalid value.
Switch51(config)# no trunk 23-24
Switch51(config)# no filter source-port 21-22