Those who don't believe in a 'Creator' still accept natural law as the basis for rights. Hard to argue with a belief system either way.
Well that belief does have a weaker tendency, but it is great that we can agree on a discover-able natural law. But the key point and concern for those of us in the 'Never Trump' or 'Trump Realist' camps is that selected judges believe both in original intent of the constitution and natural law as a basis for evaluating laws.
Not to be snarky, but I wonder how Trump would define 'Natural Law' ( image of the jungle comes to mind, remember his concept of 'Conservative').
So the nub of our sincere and deeply seated worry is that Trump would ditch the natural law/originalist doctrines when selecting judges.
After that is ditched, then we get international law incorporated into our legal precedent tree. Continental Roman based laws or ANY law from any tradition. The liberals have been pushing this doctrine for some time. After foreign law has been incorporated into our precedence tree, it take decades to overturn because of Stare Decisis or fixed precedent-- Dread Scott / Roe v Wade.
Trump never seems to be briefed on the high points, like above. Moreover, we dont have his list of judges, so that gives us pause.
Luttig, Thomas, Scalia, Douglas Ginsberg and others had these principles. We remember the intense Senate battles that Reagan and Bush had in getting these guys through or Not. Harriet Miers was also a debacle from W, so Roberts SEEMED like a miracle at the time.
It is therefore critical to have both a strong President AND Senate to maintain the real intent of the constitution. Which brings in the thread of Trump helping tea party type Senate candidates (one just lost in IN, what will happen against McCain in Arizona?)
There may be additional issues from the 'Never Trump/Trump Realist' camps but this is an attempt to synthesize the key themes in this thread.