I Know your history as well.This can't be a logic. First let them return, then I will deal with you.
I can assure you that they will.never return.
BNP isn't a problem, but Jamat is.
BNP was trapped by the greed of Khaleda Zia and Tareq Zia , so lost it's way.
Just minus these two, BNP is more secular than BAL.
BNP is a continuation of NAP of Mawlana bhasani.
Many Muslim league supporters ( who voted for Fatima Jinnah against Ayub Khan ) also support BNP.
The real problem is Jamat and it's a pro establishment entity.
In 1947 it was against the creation of Pakistan , in 1971 they were against the creation of Bangladesh, now I will not be surprised if they made a secret pact with BAL establishment.
So it's safe to say that Jamat isn't completely anti India.
If you work for them and assure them that you will help them to capture power in Bangladesh, they will work for you.
They are simply expansionist like RSS ; RSS want akhanda bharat Jamatis want Islamic rule all over the world. Both are actually same.
Bhasani was a true anti Indian and his ideology changed time to time. He was a communist to start, then collaborated with the Ayub Khan, again fireclay opposed him. And the most striking part he blessed the guy who assasinated your nations founding father. To cut short has was a non communal, mass leader who was blind with his Indian hatred's. But the most important part is his political vision was not clear.
I find BAL more of a legacy of him than BNP.
10 years back it was unimaginable that the communists will be out of power from West Bengal and nobody believed that there will be vote in West Bengal on religion and cast lines. That happened. So nothing is permanent, I know your country very well as my laws are still there. The amount hard liners are creeping there, who knows what will happen in next 5-10 years.
Between Jamat is not a threat only to BD but also to our land. Read Khagragarh.