all the first 5,000 members of the Holy Church and the first pope were not Christians at all.

Those members imply a summation into a church and under a pope...which contradicts the all father separating each child from one another. That separation process implies the christening (anointment) of each being within all of nature.

There ain't no first anything within God...only second/seco - "to divide". Holy Church implies whole God dividing/divining the body of each Christ/church.

how to fight satanism

Resisting the temptation of any suggested -ism...increases ones resistance to the temptation of being deceived. It's ones consent to any suggested -ism which shapes one into an adversary to one another.

The fight implies logic (internally) and reason (externally), with Satan implying ones free will of choice binding self to either side within conflict, which also implies becoming anti-christ, since binding self contradicts being christened (anointed).

Notice that "to fight" implies towards conflict aka turning against one another...doing that tempts one to ignore being (life) moved from inception towards death without fighting one another.