I am surprised at the anger and frustration in the responses. Don't get me wrong,you're all entitled to your feelings. I just don't see why the behavior you endure is not seen as the cost of doing business. Every type of professional in business has similar problems with clients. It's human nature. The beauty of self employment is that you can accept or reject the work you want.
A simple decline without explanation seems preferable.
Sorry, Marshall, but I am going to have to disagree with you about one thing. In my experience (though I understand that this may not be representative of the norm), giving a reason for not desiring a meeting with a gentleman leads to less abuse. If I tell a gentleman that we will not be meeting because I find his posts abhorrent, then he will either curse out in one message and be done with me or politely accept my decision and tell me to let him know if I reconsider. If I do not tell a gentleman why I will not accept him, I will be bothered by "Why?" messages for days or weeks until he then decides to curse me out and maybe be done with me if he feels like it. People feel like they have a right to know these things, and to an extent, they are right.
For me personally I am honest and it usually involves a service that I do not offer so I nicely say "I am sorry but I don't think this will work out I suggest you find an provider to meet your needs" Plain and simple and honest
The worst is when you get caught up with someone who wants to do heavy emotional processing after you decline a date. A few years ago a guy broke basically every "rule" on my site during our pre-date email correspondence (bargaining, explicit questions, and more). I told him, politely as possible, that I didn't think it would work out, and then things just got odder, culminating in an uncomfortably long email from him that ended with "I'm not mad at you, I'm mad at myself." Way too much emotional nonsense for someone I had never met. I can only imagine how much drama takes place in his civilian dating life.