You’re right to point out the conflict of interest inherent in the dealing desk model.
When operating a dealing desk, a firm may actively be taking a position in the market, which exposes the firm to market risk. When you are long, the dealing desk may be short. When you are short, the dealing desk may be long. So your losses can equate to the dealing desk’s profit. Alternatively, your profits can equate to the dealing desk’s loss. Certain strategies expose dealing desks to more risk, such as automated strategies or strategies that trade at a high frequency. To better manage their market risk, some dealing desk firms actively intervene in their clients’ trading by re-quoting orders, delaying execution, skewing prices, and widening spreads to trigger stops and discourage scalping.
What makes our dealing desk model unique is that FXCM offers both DD and NDD execution. If you are trading on DD execution and your trading style exposes us to more risk than we’re comfortable with, we may change your execution type to NDD. This is how FXCM can comfortably offer both execution options without having to resort to some of the common “dealer intervention” practices listed above which take place at many forex brokers.
I’m glad you appreciate that and have chosen to trade an account with FXCM. 
It’s possible the format of our website has changed since you opened your account, but I double checked just now and the FXCM application lets you choose your preferred execution type on the first page. However, clients are always free to change their execution type even after their account is opened, so it’s never too late if that option is overlooked on the application.