I’m not sure I buy this logic. It smacks of “if you haven’t got anything to hide, you don’t have anything to worry about” reasoning, to me. There are numerous reasons to use a VPN. For most people, that’s circumventing region blocks. Which is not illegal activity, though it may be against a company’s terms of service. For others, it’s to hide behaviour from snooping ISPs or—worse—governments, especially surrounding sensitive topics like GSM status, especially for people in less LGBTI±friendly countries.
And yeah, some people will do things that are actually illegal. Copyright infringement is probably the most popular, which I think most people on here would probably agree is not a major crime. But some smaller amount will use the privacy enabled by a VPN to do more severe crimes. I don’t know how you prevent that without limiting the privacy rights of the much larger number of users.
What harm is that?
The only harm I can see is either:
(a) by associating their users with those who use VPNs to do illegal things. Which is a nonsense association and shouldn’t be given any weight, or
(b) if they do keep logs and turn those over to authorities. Which is why companies that have been audited and shown not to collect logs, or, even better, companies that have been tested in court and unable to comply with requests for information, are the VPN providers that should be preferred.