In some Musjids, on Fridays musallis on entering at the time of the pre-Khutbah talk have to sit down and listen to the lecture.

Answer

The practice described by you is bid'ah and haraam. It is not permissible to debar people from Tahyatul Musjid and the 4 Sunnats by compelling them to sit and listen to the talk which has no relationship with the Masnoon Jumuah proceedings. It is incumbent to defy the shaitaani ban and to perform Tahyatul Musjid and the Sunnat Salaat. Ignore the talk. Do not observe the haraam bid'ah practice of the morons. If you are unable to defy the morons, then in the circumstances, it is best that you perform the four Sunnats at home.