It depends on what exactly you want to do. You don't want to ignore that nick, so I guess you probably don't want to ban or kick that nick either. How are you expecting to stop the person from spamming if you're not going to do anything to the nick?
Beyond spam detection, your bot can run a flood protection script within the script that is getting spammed. However, if it's not a mIRC bot, then you'll probably have to figure out how to write it yourself or ask on the forum for that client. For mIRC, flood protection for any type of user input that generates a bot response is to set a variable that will unset after X seconds. As long as the variable is set, halt the bot response. That makes it so it only responds every X seconds (or less).
Another option you have is to track $1 and if the nick listed there is on an "ignore" list (not the built-in ignore list), then you halt the display of the text. You'd have to have that on the bot though or else the channel will still get flooded. If you just put that on yourself, you wouldn't see the flooding, but everyone else would. In general the flood protection mentioned above is better. You'll just have to figure out how to do that with that other client.
