Can you think a situation where we deliberately want to

Can you think a situation where we deliberately want to make a species extinct? How would you justify it?

Deliberate attempt to make a species extinct was taken up by WHO in 1967 for the extinction of smallpox virus. For centuries, smallpox virus was one of the worst disease causing agents to humankind.
World Health Organisation (WHO) campaign against smallpox was highly successful and resulted in the complete eradication of this disease.
Similar attempts are being made to eliminate the HIV and polio viruses.