Android and Windows are not the most secure, it is a fact, but we should not make a mistake when reading something like that. That doesn't mean Linux or Mac are better on their own. I have tried very little Mac, so I cannot give an opinion with experience, but Linux offers 100% (something unthinkable in other systems) customization in terms of security, but still, and as I said at the beginning of this post, that does not make it better, since what really matters is the user and the experience with the operating system.
Not only does the platform matters, but also how we are using it, how our applications are written. Each system has advantages and disadvantages we can develop it or overcome dependent on our expertise and needs. Granted, Linux does have systems that make it possible to customize your settings, but only so long as you are the type that is capable of managing these settings yourself. It works the same way for Windows, Mac, or Android, where security really does depend on the user action, and not on the technology.
The first step when we try and make any device more secure is to understand what we ourselves do while using that device. For example, like regular update cheques, never installing third party software, and making use of the built in features of any system. These all can offer you enough protection that you do not have to totally rely on the type of operating system. Whether we choose the platform or not, our role as users need to be used to maintain the security.