This question is asked a lot by our Salafi brothers, to put people off following a madhab in Fiqh.
They make it seem like a person is abandoning his faith for an Imam [in Fiqh], when in fact he is strengthening his knowledge & faith by following an Imam in Fiqh.
This question is dealt with by Sheikh Mumtaz Ul Haq. For those brothers that say we are causing disunity by uploading these videos, we say, if these accusations were not put against us we would not have to refute anything, hence we have a right to defend ourselves.