If you want to protect your coins, just use a hardware wallet. Way easier and waaay more secure than an antivirus :p An antivirus isn't going to protect you from proper malware anyway.
Yes, they aren't that cheap (not expensive either nowadays) but they are absolutely worth it considering you could lose your whole stack otherwise.

You're giving the impression here that people will be safe after installing some software, you'll have to do more than that if you want to be safe unfortunately  
As you mentioned, common sense is probably the most important. A hardware wallet won't help you either if you just send coins to a scammer.