In answer to your question, I have never seen a cat be mean after using
catnip.  I used to grow my own fresh catnip (a small field--like flower bed
sized), and all the cats in the neighborhood would come and use the plants.
I eventually put up a fence, and then a second fence surrounding the first,
because the cats were reaching in and tearing out my plants.  I was growing
it and drying it as part of a cat toy business I had going.  Some cats who
don't respond to dry nip, will respond to fresh nip.  the coupe de grace for
me was when a big wild tomcat, the neighborhood bully finally came and took
some catnip out of my hand.  then he lay there rolling over from side to
side on his back, as nipped-out cats tend to do.

I still have quite a few of the cat toys (I made thousands of these things
and sold them at pet stores and vet's offices), and every now and then I
find that my cat, Arlo, has found a way in to the toys (which I keep stored
in heavy plastic bags).  some times one toy seems to satisfy him.... other
times he wants to pull out the whole bag and lie on them all!

I hope this helps you to understand catnip!

Best regards,

Mary

If there is a catnip plant on your property and it is unprotected, It won't
be there for very long!  The cats will rip it out, or roll all over it.  I
used to be able to tell by the color of the fur stuck to the plant which cat
had attacked the plant!

M