If discussions about origins were purely about how old the earth is, or who did or didn’t evolve from what, then I wouldn’t bother with the debate. The Bible does tell us to avoid foolish controversies after all (Titus 3:9) and just getting into an argument can be counterproductive.
The problem is that it isn’t just about how old the earth is or who did or didn’t evolve from what. The big concern is the knock-on effect that it can have on how you approach other areas of science. There are many areas of science where, if you don’t treat them with respect, you can end up doing a lot of damage to your career, or your health, or even putting people’s lives in danger.
Science is built on a foundation of basic rules, principles, methods and protocols, such as mathematics, logic and evidence-based reasoning. These principles are the same for every area of science, both “operational” and “historical,” and if someone is pushing arguments that fly in the face of these principles, they will be undermining people’s ability to approach every area of science that relies on them. And they have nothing whatsoever to do with “secularism”: not following the rules will cause the same amount of damage to the Christian and the atheist alike.
This is why young earth creationism tends to be something of a “gateway drug” to all sorts of conspiracy theories and pseudoscience. For starters, it is a massive conspiracy theory itself—after all, it implies that the entire scientific community, consisting as it does of millions of researchers worldwide, has been systematically lying and falsifying evidence about the history of the Earth in a tightly coordinated manner for over two hundred years. If you believe a conspiracy of that magnitude to be plausible, there are few if any other conspiracy theories that won’t be. In addition, the arguments that it presents frequently fly in the face of the basic principles of mathematics, measurement, logic and evidence-based reasoning so completely that you can lose track of what those principles actually are, or even end up viewing those underlying principles themselves as “secular” and “sinful.”
This being the case, it would be highly irresponsible and unprofessional for a trained scientist not to speak out when faced with such bad attitudes. And such a thing should be doubly offensive to a trained scientist who is a Christian, because they bring the name of our Lord Jesus Christ into disrepute. Especially when such attitudes are being promoted with the level of aggression, intolerance and false accusations that we see coming from their most zealous supporters.