No you can leave feedback after a return. If I had to return something do to damage in shipping I usually leave positive feedback if they handle the return easily. If someone responded to me like that I would return and leave a negative. If possible I would also see if you could report them to ebay for offensive or obscene language (doubt it would do anything though).
The part that gets me is the “free card holder, sleeve and padded envelope” if you’re an eBay seller this should be standard not some fancy bonus. What was his original plan? Put a raw card in an envelope and not expect a return?
It should be standard but unfortunately it often isn’t. The amount of times I have received cards unsleeved just in a envelope, sometimes without even any cardboard backing. A toploader and sleeve can cost as little as 12-13 pence in the UK for both, its frustrating but I guess some sellers aren’t collectors so don’t really understand or bother.
That guy is probably just a person selling off their old cards and they don’t really take pokemon TCG serious. Those people can be beneficial but also a hassle. I’ve had situations where I bought cards that had some flaws in the image but the actual card was basically flawless. Apparently some of these sellers just copy and paste images from other listings…very cringe thing to do but it is what it is.
Just open a return and mail the cards back to get a full refund and don’t take it personal.