With 'friends' like this, who needs enemies?
The argument appears to be that Unitarian and Free Christian are synonymous terms; "two different names for the same tradition".
In the later nineteenth century and earlier twentieth century, that could perhaps be argued. It's hardly true today. Times have changed and there certainly are "Unitarians (who are not Christians)".
It seems another example of the creeping tendency to want to brand the Unitarian and Free Christian movement with a single corporate identity and excise the bits that don't fit neatly.