That's at least a bad advice. If AV software treats a trusted download as a risk probability there are some things that might be happening:
-av software might be compromised.
-system might be compromised
-source download can really infected.
In any case av software should never be disabled. If you have doubts about the source of the download, find some friend / relative that have another kind of AV software and try to download from the same source. By doing this you're avoidint at least 40% of hack attempts.
Unfortunately, and as MegaMouse also said, Norton, McAfee, and several other a/v clients are a tad bit overaggressive, and in some ways, are behind the curve. A number of the temp files produced when the patches are uncompressed have a dollar sign ($) in the filename. Way back in the day, that character was used in malware files. This is why Norton, McAfee, and several other a/v clients flag our temp files as being malware. Malware writers are far more sophisticated now, and no longer use that character in their little gift packages.
So, when downloading and installing patch files for RoM, as I said, it is perfectly acceptable to
temporarily disable your a/v client. After downloading and patching,
re-enable the client, and you're good to go.