I actually think it was not such a bad or unscientific position for him to take, but it is certainly a remark that is easily misinterpreted. It is not Einstein's apologists that provide the intended meaning of that statement; Einstein himself was quite clear about what he meant. Einstein's only concept of "God" came in a form very similar to simply saying that God is in the laws of physics. Now, it is true that Einstein had certain preconceived notions about how those laws ought to be, and those notions both helped him come up with relativity and were galvanized by the success of relativity. They also hindered his appreciation of quantum mechanics. But it's not bad science to ask what a certain philosophical perspective on reality can give you-- his desire to find theories with certain attributes was helpful to him when such theories were effective. When they were not, it was not helpful. But that's all part of good science-- no one individual is needed to do everything, so each one can choose their own approach-- as long as reality, not rhetoric or philosophy, is the ultimate arbiter.
Actually, that isn't really what he was implying, he was implying that in his mind a scientific theory should have certain attributes, aspects that he associated with his concept of how reality worked. Yes that is a biased approach, and is not guaranteed to work, but it is more a description of something that he was looking for and would not be satisfied without, moreso than a claim about how reality had to be. It was a statement of a personal aesthetic, a search for something that when he found it, served him well, and when he did not, left him empty and unsatisfied. A double-edged sword, if you will. The rest of us are not incumbent to accept that interpretation of what physical theories should be, if we find others that serve our purposes better.

I think a fair way to classify it is a statement of a particular possibility. In philosophy, it is important to get all the ideas out on the table, and if they come from renowned thinkers, more's the better. But nothing is true by authority in either philosophy or physics-- they are just possibilities to ponder. You are right that no one should ever say "it must be true because Einstein said it". It is significant that Einstein himself said in his letter to Born "I, at any rate, am convinced that He does not throw dice." He is speaking for himself, about what he believes is the way reality works, but it is nothing but an opinion for consideration-- like all philosophy.

I can agree that Einstein had no strong argument in favor of determinism. But I also don't see the statement about God not rolling dice as being directly related to the concept of determinism. It seems to me that Einstein is basically asking, if reality needs a dice to figure out what to do, then where are the dice? In other words, a physical theory should provide all the instructions that reality has at its disposal, so if reality at some point says "now roll a die to figure out what happens", then those dice should be part of the what the theory is describing, but where are the dice in the theory? How do they get rolled, how does their output get factored into the reality? A theory that needs dice is incomplete if it can't describe the mechanism whereby the outcome of the dice get determined. But determinism is something much more, it is the claim that all the instructions for all future events is contained in the present.

To see this difference, consider a movie. When we go to a movie, we know perfectly well that the end of the movie is already determined-- it's already on the film. Yet we would never claim that all the events of the movie are somehow contained in a set of instructions that exist in the present frame that we are looking at. So what do we mean when we say the ending is predetermined? That is not the sense that the term "deterministic" gets used in science, where most people mean not that the future must come out a certain way (a scientifically untestable claim), but rather, that the outcomes are (at least in principle) predictable based on information that is encoded in the present.

Let's push the movie analogy a little farther. Let's say a famed director is known for always rolling dice to determine the outcomes of his/her movies. Does that make the experience of going to a movie by that director any different than a movie by a more conventional director, especially those not particularly known for "happy endings"? Is a movie by the dice-rolling director any less determined, when we go see it, then any other movie? The issue of predetermination, and the issue of some inherent role for randomness, are just not the same thing at all.