1: yes it is but children cannot consent and know what they are consenting to. So it's not okay.
2: Yes it is part of nature but once again, consent. Both adults should have consent. Taking it away from one party is a bad thing. As for it being "as bad as beating someone up." Well neither are allowed. Rape is worse.
3: It is not a flu, it is a respiratory virus. Just because it gives you a fever and a cough doesn't mean it's "just a flu." Yes there are deadlier diseases, no one denies that. The thing about C-19 is how contagious it is, it's long incubation period, long period where you can spread it, and that we have no cure, vaccine, or successful way to treat it. All we have are ways to slow the spread.
4: Slavery is something that as an advanced species we have grown out of. We should never justify it and should always condemn it.