EDIT: Let’s cool it with the downvotes, dudes. We’re not out to cut funding to your black hole detection chamber or revoke the degrees of chiropractors just because a couple of us don’t believe in it, okay? Chill out, participate with the prompt and continue with having a nice day. I’m sure almost everybody has something to add.
Its observed gravitational effects is evidence. Otherwise nobody would have given it a name.
Proof of gravity from an unknown source affecting an object isn’t indicative of that source’s characteristics, though.
We don’t even know if the force involved is gravity. In fact we don’t even know if a force is involved at all.
I mean yeah that’s why it’s called dark matter. Because we know nothing about it except that it has gravity and doesn’t interact much (if at all) with electromagnetic waves.