Scientists aren't charismatic showmen/women. They're more likely to be introverted, dedicated to their research and letting the evidence speak for itself.

You do not have to "defend" facts!

I wouldn't at all be surprised if some of the scientists keep quiet due to receiving threats from radical creationists.

I think it is a matter of access to media. Scientists don't have it so much, while politican swho want to appease religious fanatics do.

They are too busy doing science.

We scientists let the science do the talking. The proof is in the data. Many an extraordinary claim has failed to live up to its promise. I was involved in the Cold Fusion fiasco of the early 90s. I was paid to work on it for 2 years. The best thing that came from it is a tshirt the says 'I thought I found cold fusion, but all I got was this stupid shirt'. Science travels at the speed of a grad/ugrad working 100 hour weeks.

Many are funded by enemies of majority of human race. Job or truth simple choice for ethical and knowledgeable people , one would think.

Good observation. Scientists often complain and routinely apply for funding support from many sources. Unfortunately, there is a limited amount of financial support for the millions of researchers. Government funding is the main source for research but that is drying up rapidly since Trump took office.

Because being a scientist and being able to convey their ideas in a manner that is both engaging and understandable to the general public are two very different skill sets.
I edit a friend who is an environmental scientist's journal articles to make them more readable before they are submitted for peer review, he could talk to the general public till the cows come home about his work, which he is passionate about, but they would understand maybe one word in ten and come away none the wiser. I struggle at times and have to ask for clarification, the general public wouldn't stand a chance.
Being a public speaker or a journalist is also a skill, but a very different one from being say a theoretical physicist. Though some rare individuals manage it you can't really expect people to be both.

Science is allways talking. Papers, books, reports, documentories etc., etc,. The issue is not the takers.. it's the listeners.

Many likely fear for their jobs, and their livelihood

They get tired and irritated talking to idiots.

Because there is less money in the scientific community than there is in the religious community (the ones most frequently disputing hard science). Money wins.

Well it might have something to do with that research. It is extremely taxing. Physicists ( I imagine other disciplines do too, I’m just using an example that I know something about) who are highly active in their fields don’t have the time to debate the cosmic age of the universe with a young earth creationist because well they are busy furthering the frontier of human knowledge. Plus I think it’s enough that those who understand the value of science and fight for its epistemological superiority over other methods are doing quite well. Yes there is work to be done but the most successful efforts are those that use collaborative strategies where each member has a specialized task. For the physicist that is analyzing the results of experiments to judge either how successful a hypothesis is or the limitations of a current theory. For the science enthusiast, it is to continue advocating for a better tomorrow by encouraging more support.

Also I’ll note that these discussions do happen within the community as far as funding goes, but usually the arguments are contained in grant proposals rather than Twitter or Facebook posts.

What do people generally think about someone when that person is “defensive”? A person that is confident in their ideas will be less likely to feel a need to defend them. That may be part of it.