Technically that is correct, but if Senators are nominated then I don't see how the Senate can do its Constitutionally-mandated duty of advice and consent without being free to speak against the nominee's character if Senators feel so compelled.
I'm fine with the Senate having its rules, like this and the filibuster. Generally I approve of the Senate's rules, and on duties that are not Constitutionally mandated, I'm fine with them being as esoteric and restricting as the Senators wish. But when those rules interfere with Constitutionally-mandated duties, those rules should give way.
Personally I think Fauxcahontas is merely playing politics here, attacking Sessions' character purely to promote herself as a viable Presidential candidate. But that's my conclusion; my principles say she must be free to do so regardless of whether I suspect she's not doing so in the spirit of service. Here I agree with Warren, and even though King's letters do not sway me in the slightest, I think Warren should be free to question Sessions and point out why she does not believe he should be confirmed.