Yet we are reasonable to believe in intelligent causes existing apart from us on the basis that we perceive objects acting for teleological ends. This is not necessary knowledge.
No, it isn’t knowledge - it’s assumption that requires support. If such support is not forthcoming, then the assumption is simply that.
For example, the fact that biological organisms produce traits which only makes sense in terms of objectifying survival; it appears we live in a universe created precisely for the possibility of self moving and self producing life.
Yet only on what appears to be a significant minority of planets within the universe. Astronomers have recently discovered a planet upon which liquid water might exist, and therefore life. There is actually no reason to believe that life is, in itself, a specific case of the physical laws coming together to produce something special - we only like to think so because we are living things.
Therefore the belief that the universe has an intelligent cause is properly basic knowledge, simply because it immediately appears as if it has been designed to some degree or extent by an intelligence .
Again, I would claim in counter to your assertion that there is no reason to simply assume intelligent design because it sits happily with our perception of ourselves in relation to the rest of the universe. Order and patterns do not require intention. Intention, as we can perceive it, is a product of certain arrangements of physical entities, not a prerequisite for them.
Therefore the burden of proof is on the atheist. Simply saying that its not necessarily the case is not a valid rebuttal, because the argument is not built on the premise of necessity, but rather it is built on the premise that it is reasonable to accept a thing as true if it is immediately and consistently present in our immediate knowledge, without the need for scientific or metaphysical evidence. This is properly basic knowledge.
It might be more accurate to call it a basic assumption. Whether it is proper or accurate or reasonable to make such an assumption depends upon the state of our collective knowledge and awareness. In times past, it was properly basic to suppose that disease was spread by bad air, or miasma - this has since been proved inaccurate. Anything we call a properly basic assumption must be subject to inquiry. The burden of proof, as such, lies with those who claim intelligent design - unless there is direct evidence of a designer (that is, evidence that points irrefutably to design rather than other phenomena, and/or to the existence of an actual designing intelligence) this is not a properly basic assumption.
So long as you accept properly basic knowledge as an epistemological premise. The only way you can defeat this argument is by either proving metaphysical naturalism to be true, or by denying that things do not appear to act for a purpose.
That knowledge must have some foundation, I do acknowledge. However, I think that properly basic knowledge is more limited than your claims of intelligent design, and requires only the existence of a knower and that which is known. I cannot prove metaphysical naturalism to be true in any absolute sense - that is presently beyond my scope as an amateur philosopher. All I can do is attempt to reconcile my experience and that of others with the explanatory power of the hypothesis of metaphysical naturalism. To prove purpose, however, takes more than just the appearance of purposive action, as I indicated in my previous reply to your OP. It does require the reasonable and independent inference of a designing intelligence, a purpose-giver, an overarching intention for that which exists. Apart from these, all we can assume is that things merely
appear to act in a purposive fashion.