A sect is by definition nothing more than a subdivision of a larger religious group.
Despite that , some christian churches (in germany) like to call other religious groups (they dont like so much) sects, while they call their own groups (which they like more) churches, while the only objective difference is the amount of members in the specific group.
If you want to argue with them about it you can claim that Christianity is just a jewish sect. (provocative to some of them,but true to some extent).
When a small, non-mainstream religious group is being discussed on TV ,they usually invite a so called "Sektenbeauftragter" as an expert to give his opinion whether it is an (evil) sect or its an (acceptable) church.
The point i dont like is that this expert is always a "Sektenbeauftragter der katholischen/evangelischen Kirch" (so-called sect-representative of the catholic/protestant church) ,so a member of the bigger christian churches and therefore not objective.