I realize that if I have a wallet with 1 BTC and I receive .5 BTC, have 2 confirmations on it, spend .5 BTC and then it turns out that transaction wasn't legit I will just end up spending .5 of my original 1 BTC.
Not really. It depends.
For any ordinary transaction (not block generation), there are inputs and outputs.
If you use your "1 BTC" as an input to create a transaction of 0.5 BTC, you will left with a 0.5 BTC change.
If you use your "0.5 BTC" as an input, and that incoming transaction has been double-spent, your 0.5 BTC outgoing transaction will never get confirmed as well, and you will left with your 1 BTC.