Agree that your first line should be "I don't want to meet up with you" rather than "I'm busy" or making excuses. Then block the guy. If he comes back under another name, tell him to stop. If he continues to harass you after you have made it clear to him that his approach is unwelcome, then is the time to go to the police, as you will be able to show that you have made reasonable steps to avoid him and you have specifically told him to stop, yet he is still pursuing you.
As it stands, nowhere in that conversation have to told him to go away or that you will not meet up with him. Ever.
You don't have to meet with him to tell him to stop. In fact you shouldn't, because if he's as twisted as you say, that could encourage him to ramp up the harassment or claim goodness knows hatever against you. It's best to do it in writing where there will be a permanent, preferably publicly visible record which is not open to misinterpretation.
RE: What's annoying you today? V4