I personally am not saying that there are too many Jews on the Supreme Court, and I would like to make that clear right now.
However, I do think that there may be too many Catholics on the Supreme Court. Now I don't think there shouldn't be religious people on the Supreme Court. However, I do think that if we have so many religious people on the Supreme Court then we should have at least one Justice who is agnostic or an atheist.
The reason being is that, theoretically, you are in right in that the Justices should be unbiased. However, realistically, it is next to impossible for anyone to be totally unbiased on an issue. Especially the controversial issues the Supreme Court rules on.
Take, for instance, one thread I read on this debate forum. It was a link to a news site saying that Chief Justice Roberts believes he has found ways in which Roe v. Wade can be overturned. Now, I don't think it's the purpose of a Justice, especially the Chief Justice, to state how he can decide a case that hasn't yet been brought up before him. I also don't think that it's a coincidence that Chief Justice Roberts is 1) conservative, 2) religious, 3) Catholic, and 4) believes he could rule against abortion in the United States.
So whether you want to admit it or not, a person's beliefs does affect their judgments, whether those favor conservatives or liberals.
Which is why in a constitutional democratic republic such as ours it is important to give weight to diverse array of opinions.
Now you are correct in that Congress is the primary government body by which our nation achieves the most diversity. However, you also have to remember that Congress
1) Has 535 members
2) Has terms of 2 years for the House and 6 years for the Senate
This means that not only is power in Congress diluted, it is rather easier to kick out unwanted, unethical, or unpopular Congressmen.
The Supreme Court, however, has more concentrated power because
1) It has only 9 Justices
2) Appointments to the Supreme Court are lifetime appointments.
That means that power in the Supreme Court is far more concentrated and it is more difficult to kick out unwanted, unethical, or unpopular Justices.
And the reason why this is a concern to me is because I believe that all people and groups look after their own interests than the interests of others. I also believe that the Founding Fathers designed our three branches of government with that in mind, and would prefer a balance in the branches to ensure every interest has a say in government so that no one particular interest unduly interferes with the rights of those with other interests.
For example, while employers have rights in this nation, so too do workers have rights. Why? Because both have the right to vote.
That's why I would like to ensure that there is a diversity on the Supreme Court. I think that because the Supreme Court has the power of judicial review over Congress and the Presidency, it is even more important that there is a diversity of interests for the highest court in our nation. That way, the Supreme Court as a whole will be better able to discuss, debate, and finally rule on matters of law in our country.
Now I'm not saying that every group should be represented on the Supreme Court. That is quite unrealistic, and I don't think we should have any kind of hard quota system. However, I do think that when a new seat opens up then the next appointment should be one that brings an added diversity or increased balanced to it, and diversity and increased balanced on multiple levels.
For example, all the Justices are religious, and the majority are Catholics. However, they rule on issues that impact religious people along with atheists. So I ask why not appoint someone who is agnostic or atheist?
However, I don't want that to be the sole reason of appointment. I also think that there are too many Justices who have been giving too much power to the Presidency, and one criticism of Kagan is that she supports providing more powers to the executive. So not only would I want someone appointed who is agnostic or atheist, I also want someone who bolster the power of Congress to act as a check on the President.
But that's not what we get, realistically. What we realistically get is an appointment who will support the policies of whichever President nominates them and the Senate doesn't mind too much. And I, for one, think that giving lifetime appointments for short-term judicial justifications is worse than having a quota system for SCOTUS.