I can't officially speak for this product anymore, as I'm no longer involved in its development, but...
False positives are becoming more and more common with certain virus scanners, and it's possible that this is happening to you. Another possibility, and probably more likely, is that you have other malware or virii on your system that is attaching itself to anything you download.
I just downloaded a fresh copy of the Sex Sim installer from here and ran a MalwareBytes check on it and a BitDefender check on it, and both reported no threats found.
I would do a total virus check on your system, as well as scan the system with MalwareBytes (it's free) and SpyBot Search and Destroy (also free). You can find them both in Google, but make sure you get them from the actual sites they are from.
I hope that helps!