Of course not, if they put Maria Cantwell in office then it is their right to crow about her anti social conservatism and strut their third party strength to move the country left.
They didn't put anyone in office in that particular election if you refer to Libertarians.
The VOTERS put Maria Cantwell into office. It is obvious that a majourity of the voters preferred Cantwell for whatever the reason.
If the opposite majour party candidate did not sufficiently appeal to the voters, this is not the problem of the Libertarian party. It is the problem of the REPUBLICAN PARTY candidate selection mechanism. (Assuming that Cantwell is a Democrat, i really don't know).