It is possible that LDView creates antialiased screenshots when running on certain video cards. It's been so long since I worked on that code that I honestly don't remember. But Philo's suggestion to render larger and then down-sample with a graphics program is really the only way to be sure. Note that if you have edge lines enabled, it's best to set their thickness to a value greater than 1; otherwise they'll be really thin in the scaled-down image.
There are two other things you can try. Set the "IgnoreVBO" setting to 1. You can do this either on the command line using -IgnoreVBO=1 or in the registry. Search for ZoomMax in the LDView help file until you get to the part where it tells you the registry value to create. Change "ZoomMax" to "IgnoreVBO", and set the value to 1. If that doesn't help, then after you have done that, check the "Don't use Pixel Buffer" option in the Save Snapshot dialog. (The corresponding registry/command line setting name for that is IgnorePBuffer.)
Please note that if you have both of these things set, then LDView will actually draw the snapshot into a hidden buffer on the screen, so any other windows that obscure any part of the LDView window at any time during the snapshot save can cause problems (which is why it doesn't do it that way by default).
There are two other things you can try. Set the "IgnoreVBO" setting to 1. You can do this either on the command line using -IgnoreVBO=1 or in the registry. Search for ZoomMax in the LDView help file until you get to the part where it tells you the registry value to create. Change "ZoomMax" to "IgnoreVBO", and set the value to 1. If that doesn't help, then after you have done that, check the "Don't use Pixel Buffer" option in the Save Snapshot dialog. (The corresponding registry/command line setting name for that is IgnorePBuffer.)
Please note that if you have both of these things set, then LDView will actually draw the snapshot into a hidden buffer on the screen, so any other windows that obscure any part of the LDView window at any time during the snapshot save can cause problems (which is why it doesn't do it that way by default).