Actually, the Constitution states:
... he shall nominate, and by and with the advice and consent of the Senate, shall appoint ... judges of the Supreme Court, and all other officers of the United States, whose appointments are not herein otherwise provided for, and which shall be established by law:
Federal Appeals judges being an "other officer of the United States". Note that nowhere in this does it say on what basis the Senate shall make its advice or grant or withhold it's consent.
Your premise that the Senate is supposed to advise the President and grant or withhold it's consent based on whether or not the candidate is qualified is not backed up by the wording of the Constitution. There are no limits or guidelines in the Constitituion regarding the basis on which the Senate can exercise this power.
There are legitimate reasons for opposing the Senate's actions regarding this man, but none that I can see that are based on the Constitution.