Linux based operating systems are more secure for a number of reasons, such as privelages and access rights, the culture surrounding it and the type of users which use it.
Linux has a strict set of access rights and privelages which is one of the main reasons for it being less prone (but not completely secure) against virus attacks. On Windows operating systems, users are normally given full rights and thus programes can be executed as that user, or with a simple click of the "I Allow" button the software can do a lot of damage.
With Linux, software and programes, users and anything installed is automatically given a low set of privelages and it requires the explicit command by the user to allow a program to do something.
Culture is another important factor, the majority of Linux operating systems are open source which means any problems are immediately identified by someone around the world. This differs from proprietary operating system which rely on a single company to find and fix the problems.
What this means in terms of prevention against viruses is that Linux is going to have that security patch a lot more quickly than another operating system will.
Finally, the type of user is more important. Windows computers are by far the most commonly used operating system and therefore the market is prone in itself. You have those who are experienced, but the majority are families, children and those who don't know what a firewall is. The inexperience of these users often leads them prone to phishing attacks, the clicking of malicious links and generally low PC maintenance which makes them easy targets by hackers. This is inevitable because of the sheer number of Windows PC users.
With Linux on the other hand, the general demographic of the user is someone who has some experience with computers, and therefore isn't as likely to let a piece of software run if they don't know where it is from.
But as always, FIREWALLS, ANTIVIRUS and NEVER TRUST UNKNOWN SOFTWARE. Follow these rules regardless of the operating system and you shall be fine!
And yes, there are a large number of good A/V scanners for Linux, since Linux systems with these scanners are used for most network-edge and email scanners. Most frequently, they are used to scrub data being sent to Windows systems...
Free: ClamAV (known as ClamWin on Windows systems). A good, open source A/V tool available for just about any system today, including Windows, Linux, and OSX.
You are very much right in your post, AHarrisGsy; while Linux isn't free of malware, it should be noted that the amount of malware, viruses etc. for Linux is absolutely miniscule compared to the number for other operating systems such as Windows.
But you are stll right in saying what you did.