is permissible for the Imam to start the Salah few minutes before the stipulated time of the Masjid for some important reason.

I am the Imam at a Masjid in USA. I would like to know if it is permissible for the Imam to start the Salah few minutes before the stipulated time of the Masjid for some important reason.

There was a lecture of guest Aalim after Maghrib Salah at our Masjid. He drove for 4 hours to come to our Masjid. There was dinner after his Speech. The arrangements for dinner were made in the Parking Lot of the Masjid. The speech finished at 7:25. The time of Isha starts at 7:28. The time of Jamaat was at 7:45. Since it was very cold that night and people had to eat in the cold, and also because the guest Aalim had to drive back after Isha for 4 hours, and also because most of the regular Musalli of our Masjid were present at the Masjid plus over 150 more Muslims came to listen to the speech, I took Mashwara from the Musalli's whether we should pray Isha Salah right after the Azan. The people said yes. But when I when I was about to start the Salah a person started yelling in the Masjid that we must wait till 7:45.That person also made some derogatory comments for the Imam.

In the circumstances mentioned above, do I have the right to what I did after taking Mashwara from the Musalli’s.Is yelling allowed in the Masjid? Can a Musalli insult the Imam, like this and later pray behind the Imam?