Meanwhile people say "But the homeless people will just use public wifi for porn!"

Like... okay, and what are you using your wifi for?

Regardless, removing this would just make them more stressed and irratic. There are worse things than legal porn on public wifi. If this tradeoff means 1% of them feel relaxed enough to actually do a job search afterward, and get motivated to get money for a more comfortable, more private place, then it's worth it.

But this is all a red-herring and not the real issue.

The lack of a panacea--a silver bullet solution to homelessness--does not mean all our resources are just a suboptimal waste. These incremental improvements are worthwhile when the cost tradeoff is so tiny (e.g. an internet modem with a properly configured firewall basically runs itself)