There's nothing wrong on your network layout. Basically, this issue comes up since you and the home viewers are sharing the same TV source (cable box, DVR or satellite receiver).
There are three options for you to try if you want to "fix" this issue. First, get a dual tuner box. This option will allow you to ''split'' the TV signal coming out from your TV source, without affecting to home viewers. You only need to connect the Slingbox to the TV option designed for IR (Infra Red) signal and the TV set to the TV option designed for RF (Radio Frequency) signal.
Second option is to get a box dedicated for the Slingbox. In this case, you will set up the Slingbox in order to control this dedicated device, withouth affecting home viewers.
Finally, using your current network layout, you need to set a splitter on the cable that comes from the wall. This way, you will be able to send two lines: one for the Slingbox and the second to the TV source. The only disadvantage for this option is that you will get on your Slingbox the channels you get through the basic cable signal.