Do What You Can
Answer: The Chafetz Chayim dealt with such a question by providing a parable:
"A man saw a bridge collapse, hurling twenty people into the river below. All of them were in danger of drowning. Two onlookers jumped into the water to rescue them. Just then they heard a fellow shouting:
'Fools, what good is your jumping into the water? Can you save everybody? There are only two of you and twenty people have to be saved. You better give up!'
Of course they laughed at this 'wise' man. Isn't it worth bothering for the rescue of only two lives — or even one? Even if it is hopeless to save everybody is it right to just stand by and give up on those who could be saved?
A person must always remember that he has a duty to do whatever he can in order to help and in order to save."