It is not unusual for companies to have as part of the job requirements for outside sales or positions representing the company where a certain image was desired, a decent late model vehicle, typically needing to be a newer than a certain number year. Normally, there is a stipend provided to be used for this.

If a contract was signed, or this requirement was included in the job requirements at the time you were hired, you are on the hook to do it or move on. If this was a complete surprise or had never been an issue for anyone else, maybe you need to have a discussion with HR to find out what's going on. Maybe the company needs to provide you a vehicle that they deem appropriate for their representative to be seen in.

If this is not an outside position and they just don't want a piece of crap on their lot, then you have to decide if you want to fight this or figure out why they want to get rid of you.

ETA...Twitter? The garbage can of America? Probably BS.