Thanks, barefooted, for posting the link you did, and artappraiser for your comment on it.

AA you wrote:

But that is the essence of true conservatism, isn't it? To believe there are certain core truths that man must follow, good bad or indifferent.

I respectfully disagree.  Part of conservatism's essence is in asserting the value of some of our values, traditions, institutions, norms, etc.  But conservatives don't so much insist on certain core, timeless truths as insist that before a community or a society supports changes it might otherwise oppose or decline, it is essential to consider which among those values, traditions, institutions, norms, etc. that are judged important to preserve could be overly compromised, weakened, or lost.  This is in part because while change is a constant, the nature of change is not, and change is neither inherently good nor inherently bad, in terms of what human societies and individuals value.    

I don't understand conservatism as implying that what is presently valued by the conservative is necessarily viewed as of timeless or universal value.  Conservativism can be entirely compatible with ready acceptance of cultural variation and relativity in norms and practices--as anti-fundamentalist in this sense.  (In fact, conservatism can counsel against efforts to change norms and practices of other human communities.)  And conservatives sometimes do not oppose change, but oppose proposed or potential changes viewed as too rapid or too broad in scope, sometimes supporting smaller, more modest or incremental change instead.  Some conservatives are full-fledged believers in evolution--they just want a slower, more gradual pace for it than some others favor.  

I would venture to say that many of us at dagblog who find Trump and Trumpism so dangerous and objectionable do so in part because we believe that at least some among our more established norms, traditions, practices, etc. of government and the conduct of the presidency which he is shredding are valuable and important to preserve as bulwarks against tyranny and other abuses of power. In this sense probably most if not all of us have some "conservatism" in us.  

I think of "reactionary" as taking conservatism to the extreme by in effect presuming or asserting that any and all change is bad and that what we need to do is go back to real or imagined earlier arrangements.  Whether the asserted earlier arrangements were really as the reactionary represents them is another matter.  Very often a highly incomplete if not a factually false picture of that imaginary past is what is presented as what we need to go back to.  And whether there is any viable way to go back to the presumed better past is another matter as well.  

The word "fundamentalism", as I understand (or misunderstand) it, seems to come closest to describing the stance you referenced: "To believe there are certain core truths that man must follow, good bad or indifferent."  I share your aversion to it.  It is typically anti-relativistic both across time and across space.  Usually the cited authority for the averred timeless truths is either a text viewed as sacred or a private communication wherein the Almighty is claimed to have revealed to the fundamentalist said truths.  Issues with reliance on either are well understood by folks here and don't need elaboration. 

It might seem as though I am being picky.  But I believe these are important distinctions, whether or not you or others use the above terms in the ways I tried to describe above.