The Nigerian system and heartless men in power will force you to carry arms no matter how peaceful you pose to be.

Going to the past after the civil war, the Niger Deltans peacefully protested and were masacred. But that now gave birth to another strategy. Before they became millitants, they were forced to carry arm due to how they were treated and because carrying of arms was not their main intention, they accepted armnesty for peace. Kanu came up again with the Biafran idea. We all know how he ended up carrying arms indirectly. Any group (boko haram, bandits, iswap, etc) against peace will rubbish the call for armnesty.

Since previous government attempted the dialogue style and it worked. Why can't the present government adopt same strategy towards those agitating for referendum? Why the use of force?

Because they think we are still living in the past

Seeking referendum is carried out via your state and region's govt apparatus, then presented to UN and NG government. Your referendum will not be done for you by Buhari, your state governors, your state house of assembly are the ones to carry out a public vote, to see if actually all Ibos want biafra, for instance...the truth is not all Ibos want their own biafra state, and not all yorubas want to leave Nigeria, most want autonomy and true federalism, which also need to be pushed by our lawmakers(representatives), in Abuja. All of us just need equity and justice, think about those that still want to be part of Nigeria in those state. The referendum route starts within your state. Government reacts when violence and guns are involved.