There is a right way and a wrong way of responding to Literal Six Day Young Earth Creationism.
The wrong way: object to their religious presuppositions.
Do not object to them introducing religious presuppositions into science. Do NOT object to them introducing religious presuppositions into science. DO NOT object to them introducing religious presuppositions into science. As soon as you’ve gone down the route of objecting to their religious presuppositions, you’ve lost the argument.
This is because YECs believe that you are motivated entirely by presuppositions and biases of your own. The fact is that there is a very real anti-Christian bias evident in many parts of academia, culture and society. It may not be quite as caricatured in the God’s Not Dead movies, but it’s very much there, and young-earth creationists automatically assume that it is the main, if not the only, reason why they can’t get creationism taught in science classes in schools.
Even if you believe this perception to be illusory, by framing the debate in terms of religious presuppositions, you are just confirming it. This adds fuel to the fire, causes them to dig their heels in, encourages other Christians who are “on the fence” about the whole matter to join them in the young-earth camp, and can make scientifically literate Christians, who are best placed to bring correction on the matter, reluctant to do so.
On a similar note, do not describe yourself as “opposing creationism” or “combatting creationism” or “arguing against creationism.” By expressing opposition to creationism itself you are giving yourself the appearance of being motivated by your own presuppositions again. You are also giving the impression that you would not take them seriously even if they did manage to come up with rock-solid, indisputable, watertight evidence to support their case.
It especially makes me cringe when I hear Christians making this objection. This is an objection that is very easily misunderstood, and you can all too easily end up sounding like a non-Christian when you’re making it. It also opens you up to charges of “compromise” — a favourite YEC accusation. So be careful.
Furthermore, if the only problem with YEC were religious presuppositions, then the evidence would be ambiguous, and it really would be possible to look at it through different “glasses” and see six thousand years rather than 4.5 billion.
The right way: demand that they get their facts straight.
What you are to oppose, combat, and argue against, is sloppy thinking, falsehood, unjustified assertions, and resistance to critique. As such, your response to young-earth creationism needs to be simply a demand that YECs get their act together and start applying the same standards of rigour and quality control as everybody else.
For this is the real problem with young-earth “creation science.” Their technical standards are so low that in any other area of science or technology, they would kill people. They are at times willing to tell outright falsehoods in order to support their position. They refuse to be held accountable to anyone outside their own echo chamber. And they show a cultish hostility to critique even from concerned Christians who share their stated goal of seeing the Bible upheld as the Word of God.
Most rank and file YECs aren’t even aware that this is an issue. When I tell them that science has rules, their natural tendency is to assume that I’m talking about a rejection of miracles. I have to make it clear to them what kind of rules I’m looking for, and that rejection of miracles has nothing to do with it. No arithmetic errors, no quote mining, no fudging of the data, no misrepresentation, the need for adequate peer review and replication, and so on. Basic standards of honesty and quality control — and furthermore, very much in line with what the Bible itself demands in terms how we handle weights and measures (cf Deuteronomy 25:13-16; Proverbs 11:1). I say that to break these rules in order to “fit Scripture” is neither scientific nor Scriptural. Yet time and time again, I see young-earth arguments that completely disregard these rules, and then cry “compromise” or “persecution” even over mistakes as egregious as misquotes, arithmetic errors, and cherry-picked data.
The fact is, most YECs agree wholeheartedly with these rules in principle. They just aren’t aware that bad arguments from the young-earth camp are a problem — mainly because many of them lack the scientific and technical understanding to be able to fact-check them.
Addressing the issue of quality control is hard work, to be sure. You have to make sure your own facts are straight as well, and it can also be difficult to communicate the nature of the problem clearly and in an easy-to-understand way to people who very often have little or no scientific training. But it is very, very necessary.