Dealing desks brokers try to group the trades together not sending tiny individual trades to the market the way the ECN brokers do. The goal is to save on the broker’s transaction costs. This is something that the tourist agency does when they assemble a tourist group to Hawaii instead of selling the tours individually.
The dealing desks have an option not to hedge the customer. Only in that case the trader “losing” means the broker is “winning”. However, reputable regulated brokers customarily hedge their customer trades. Even unregulated brokers will not hunt stops and try to make you lose. They don't bother. They know that many forex beginners will beat themselves without any help.
There are numbers of benefits to dealing desk brokers such as no delay in execution and no re-quotes. Therefore, it is not a simple black and white issue and there is no absolute advantage of the non-dealing desk brokers despite what many forex advising sites have to say about it. As far as the USA based companies are concerned, the accusation that dealing desk brokers manipulate the quotes is absolutely untrue.
Every regulated broker is controlled by a system called FORTRESS (Forex Transaction Reporting Execution Surveillance System) implemented by the CFTC and NFA. The system logs every single trade by every single customer and the time it was executed. The files are submitted nightly to the regulators. The dealing desk brokers which are manipulating the prices will be easily spotted by the system and the brokers would be disciplined or even closed by the NFA.
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