Progressives are working hard to make unapologetic conservative Christianity unacceptable in the public life of our nation.
You perhaps think your identity as a Christian is essential to your identity and actions as a citizen, because—though Christ’s kingdom is not of this world—you are a Christian citizen in a country that is made a nation by the rule of “we the people.” Thus, being your authentic self just like a good liberal, you believe you are your best as an American when you don’t hide your faith in public, especially in participating in political life. You are a good citizen because you try to be a good Christian, and it wouldn’t occur to you to pretend that’s not the case. You probably think America has been “a Christian nation,” or at least had a Christian society, and that God has blessed this country.
I find that this type of connotation/denotation blending is really common among leftists, at least in internet circles. An extremely benign academic definition is used to paint labels, but then it's rhetorically matched with informal understanding as a pejorative term.
Do you mean like when people say things like "international bankers" and they really mean Jews, or when Reagan talked about "Welfare queens" and a "strapping young buck using food stamps" and he very clearly meant black people?
Or like when people say "border crisis" or "illegal immigrants" they are actually saying "OMG you should be afraid of all the violent ethnics coming to rape your white women!"
That's because the academic definition sets the limit of the term, while the informal understanding connotes the damaging practice.
People on the right do it, too, but worse. Take critical race theorists as the prime example. The term refers to an incredibly small subsection of academics who combine critical theory with critiques about race. And somehow, this minuscule aspect of even legal academia is everywhere all the time.
I personally don't have a problem with connotation/denotation blending. Christian nationalists were studied because some academics found their beliefs interesting enough to study. And it was interesting to study probably because they didn't seen Christian nationalism as extremely benign. They wanted to systematically survey the danger that the belief system represents.
Fascism has an academic definition, too, and it's been studied a lot since its inception. Fascism is a dangerous ideology. A systematic inquiry into how it operates can help those who love freedom push back against it.
The difference between the left and the right isn't whether the blending occurs, but that the right isn't disciplined in its use of the method. You don't see leftists disparaging Trump a Christian nationalist like the right calls regular history teachers critical race theorists. Instead, they leftists rightfully call Trump a fascist, while the right manufactures and exploits racists fears about white subjugation or even extermination in a pluralistic society.