I don't think the phrase “evidence mounts” means what Fox News thinks it means. Check out this headline on FoxNation.com:

Now, if you click through, you get a Fox News article headlined “Tea Party Protesters Dispute Reports of Slurs, Spitting Against Dem Lawmakers.” So the “evidence” turns out to really be “denials by people who may or many not be in a position to know.” And not even that, in some cases.

The article purports to offer exactly two pieces of “evidence” that Democratic members of Congress were not the target of slurs. Neither is compelling.

Fox's first piece of “evidence” is a Tea Party activist who says he didn't hear any slurs. But the Fox article didn't provide a single reason to believe the activist would have heard such a slur if it was uttered -- the article didn't say he was present at the time of the alleged slurs, for example. It just said he attended the protests -- along with thousands of others.

Fox's second piece of “evidence” is ... another Tea Party activist who says she didn't hear racial slurs, according to Fox (Fox doesn't quote her on this point.) But this activist, Kay Fischer, actually confirms one of the slurs -- that Barney Frank was called “faggot,” though she asserts it was soma sort of set-up.

Further, Fox's account of the controversy ignores the actual offensiveness of the slur “faggot”:

Though reporters heard someone call the Massachusetts Democrat, who is gay, a “faggot,” and Frank and House Majority Leader Steny Hoyer publicly condemned the slur, Fischer said the incident was not so cut and dry.

Most importantly, Fischer said Frank was the first to start using salty language.

She said she and a half-dozen other protesters were waiting outside a committee room in the Longworth House Office Building on Saturday for about 45 minutes when Frank finally emerged. He was mobbed by reporters, she said, and the protesters started shouting things like, “Kill the bill.” Then she said Frank snapped at them.

“He looked at me and said, 'F you,'” she said. [Emphasis added]

But it isn't particularly important whether “Frank was the first to start using salty language.” Someone calling Barney Frank a “faggot” isn't noteworthy because it's “salty” language, but rather because it's a bigoted slur. “F you” just isn't comparable to that, even if Frank said it. I suspect most people would be more upset by someone yelling a racial or ethnic or religious slur at them than by someone saying “F you.” I would hope Fox understands this, even if they pretend not to.