system
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Uhhh, it does not do that (in my experience) unless you are currently infected. So, you might want to think about that. 
To answer your question directly; You don’t. Its not a “nag” when you are infected and you AV is telling you what you should do. No more than police forcibly stopping a bank robbery is tyrannical or facist. It is doing what it is supposed to do.
Now, if you want to see about getting your likely infection cleaned, see here>>http://forum.avast.com/index.php?topic=53253.msg451454#msg451454