The choice in Islamic law is that non-Muslims who are not People of the Book must convert to Islam or be warred against. “Kill the polytheists wherever you find them” (Qur’an 9:5) applies here if they don’t embrace Islam. So even allowing them to leave the country is, from the standpoint of Sharia, letting them off easy.

“Afghanistan’s Sikhs to ‘make choice between converting to Islam or leaving country’: Report,” ANI, October 22, 2021 (thanks to The Religion of Peace):

October 22 (ANI): As the security scenario in Afghanistan continues to deteriorate, Sikhs — a community that was already in a dire situation before the collapse of the government — practically have to make a choice between options of “converting to Sunni Islam or run away” from Afghanistan, said a report.

The community, which once numbered in the tens of thousands, has been ruined and devastated by years of emigration and death, driven by both systemic discrimination and an uptick in fanatical religious violence in Afghanistan, International Forum For Rights and Security (IFFRAS) said.

The larger numbers of Sikhs live in Kabul while some in the provinces of Ghazni and Nangarhar.
On October 5, 15 to 20 terrorists entered Gurdwara (Sikh temple) and tied up the guards. The attack happened in the Kart-e-Parwan District of Kabul. Sikhs in Afghanistan often experience such attacks and violence in the country.