While the two make a point of saying they have no opinion about the legality of Google's practices, their questions for Google representatives in the Senate hearing made it clear they have problems with the company's policies. Lee went so far as to accuse Google of fixing search results.
The letter also addresses the issue of mobile search, pointing out Google's success in that area. While acknowledging a Google statement that they do not require their products to be installed on Android devices, they senators suggest the FTC should be proactive in somehow requiring that.
In fact there is no reason to believe this is an issue of any kind. The most successful Android tablet made so far, the Kindle Fire, replaces Google apps with Amazon alternatives and clearly favors Amazon services as well.
The reality is, there is no legal requirement that Google help their competitors. There is also no legal justification for demanding their search results be unbiased. Likewise, they have no legal obligation to promote competing services.
The purpose of antitrust laws is not to prevent a company from being too successful. It is to ensure successful companies are not allowed to prevent others from being successful as well.
Read the letter in its entirety below: