Agree, the Internet was built on the premise of: be liberal with what you receive, and conservative with what you send.
Please do not accept invalid events in your client. Do not accept non-integer "created_at" values, do not accept non-string-array on "tags", do not accept bech32-encoded keys as tag values. Every time you do that, Nostr dies a little.
For more information on how this kills Nostr, read https://fiatjaf.com/27598e6f.html