You make your own problems in this business, and just by having that sort of a discussion with such a recalcitrant tenant, you are creating problems for yourself, and I’m sure you are finding your conversations are already getting personal and nasty.
You simply, absolutely, positively, must enforce no-pay, no-stay. These tenants of yours are really bad actors threatening you that way. Get an attorney to advise you this first time. After that, you’ll know how to handle an eviction legally and to your State/County protocol.
You’ll probably need to mail them (certified mail) a demand letter for rent. They’ll probably refuse it at the Post Office, but not to worry, you just need to follow the rules so you can tell the judge when you go to court in a few weeks. Evict this tenant ASAP.
There is a 50/50 chance they’ll actually come up with the rent when you make them respect the law. You can then choose to keep them (or may have to depending on your local law), but if they don’t pay, then they will be out of your hair fast. You’ll call the Sheriff a few days after court (as the law provides), and they’ll come remove the resident. They’ll then have 30 days or so to remove their trailer. (But that that point they may sell it to you or someone else who will keep it in the park, rather than take a loss and have to move it.)
But no matter. Just don’t make any more headache for yourself. Don’t have any more conversations with a tenant like this who threatens you. Let your attorney take it from here. You won’t even have to see them in court. Your attorney will go to court and get them out for you.
Word will spread in your park FAST that you expect the law to be followed, and no one will try this stunt on you in the future. Remember, you are not doing anything illegal or unkind. These tenants have threatened you (breaking the law), and it is they who are not paying rent (again breaking the law).
Let your attorney take it from here, and get them out.