It strikes me that there is a distinct division between the secular and religious anti-Leftists (groups who often get bracketed-together due to their sharing an enemy).
The secular 'Right'* (including most of the Alt-Right) regard mass immigration to The West as the most important current issue; that issue which needs to be addressed first and with the greatest urgency.
In contrast, Christian anti-Leftists (such as myself) regard the sexual revolution as the most important current issue.
(Although I also argue that this is an issue that cannot be effectively addressed until after there has-been a Christian revival - thus a religious awakening is the issue that needs to be addressed first and with the greatest urgency.)
So the seculars and Christians are applying a different Litmus Test.
The secular Right often judge Christians to be soft on immigration, hence covertly Leftist; while the Christians regard the secular Right as wobbly on the sexual revolution - often advocating extra-marital promiscuity - and therefore as in-essence Leftist.
Since there can only be a single priority; Immigration versus the Sexual revolution makes a useful Litmus Test to evaluate the true status of an anti-Leftist.
*I use scare quotes around the word Right, because I regard the secular Right as being in fact a variant of The Left - since their ultimate judgment is in terms of hedonic satisfactions. Both are materialists/ positivists; and the only significant difference between the Secular 'Right' and the mainstream Left is a disagreement concerning the best or most effective ways to maximise happiness or minimise suffering during mortal human life. Whereas the Religious have a different ultimate evaluative reference that goes beyond the gratifications of mortal human life: i.e. for Christians the salvation of the soul and its progress towards greater divinity.