In some languages the literal translation of "so called" usually has a neutral connotation. E.g. in the Czech language you may very often find a sentence like this (literally translated from a Czech newspaper, not a genuine English text):
1. The government approved exceptions for so called non-pedagogical workers.
Here the "so called" means that what follows is a terminus technicus, a domain specific jargon.
Only sometimes (in the Czech language) in a very specific context it has a negative connotation (and is usually marked with quotation marks in written form or by showing the quotation marks by two fingers of both hands or by changing the intonation in speech):
2. The government does not accept the result of the so called "referendum" in the East Ukraine.
However, I read a recommendation in an English textbook not to use "so called" as it almost always has a negative connotation in English, like in my second example.
The book was written by a native English speaker who had lived for many years in my country and wrote recommendations specific to our locale. In my language we use "so called" by default with a neutral connotation and we usually have to mark a negative connotation somehow, e.g. by intonation. The writer of the textbook, however, advised against using it in English as its default connotation is negative.
Is it true? Do you as native speakers perceive it the same way?