I don't think that's fair. I think recoiling from criminals is a much more natural reaction than the woolly liberal one.
Also, I consider myself pretty left leaning in politics but one thing I hate about the left is how some try and act like those who don't agree are below their own intelligence or are not wordly enough to understand where the more liberal view might stem from. It's the sort of attitude that makes people retreat further into any right-wing views they might have rather than getting them to see whatever light you want them to see.
But sometimes people really are exhibiting lack of intelligence. This case is an example; prisoners families are not themselves guilty of any crime and suffer as a consequence of actions they didn't commit. Anyone who can't see this is being singularly obtuse.
Interestingly, not all right-wing people do take the same view on this. I have no love for the Daily Mail, but they've done a far more balanced piece on this story than the Sun; they mention the hostile tweets, but also mention the supportive ones and clarify that these greatly outnumber the hostile tweets. Their comments section is also mainly supportive of the donation.