It's not just what "it" is called; what "it " means in the first place is something else that people cannot agree on.
Usually the people arguing that there is no agenda mean that there is no SPECTRE-like global conspiracy headed up by a shady Mr Big, with reach that extends to referees, the media, UEFA, FIFA and beyond whose sole ambition is to thwart the plans of Manchester City.
Usually the people who argue that there is an agenda mean that a number of individuals and bodies in different spheres have ulterior motives and vested interests in producing output that is either contrary to the the interests of Manchester City, or which promotes Manchester United at the expense of its closest and fiercest rivals (principally, Manchester City) or both.
Both schools of thought seem to me to be entirely valid.