Priority setting is ignored when applied to a label or multiple torrents at once about rtorrent HOT 1 OPEN

It sounds like you're asking this question in regards to working with ruTorrent instead of the native UI, but luckily there is a way to do this with the built-in commands. All of these next commands are meant to be run from the Ctrl-X prompt in the native terminal UI.

This will set the priority to "off" for all files for all torrents:

d.multicall2=main,"f.multicall=,f.priority.set=0"

If you wanted to just try turning off all items' priorities, you can do this instead:

d.multicall2=main,"f.multicall=,f.priority.set=0"
# It can take a bit for the traffic to actually die down after after setting the priority, which is what you may have seen, so you can stop/start the torrents to force it to take effect.
d.multicall2=main,d.close=
d.multicall2=main,d.start=

If you don't have access to the terminal UI, there are programs like xmlrpc-c or pyrosimple's rtxmlrpc that will let you issue commands over the XMLRPC interface (full disclosure, I maintain pyrosimple).

from rtorrent.