I really don't get people vehemently against this.

You seem to be making arguments against PF Farm parties excluding people that haven't done it before. That's not really the topic at hand. The topic is about a tool which would, as many others stated before, prevent people from lying about if they did it already or not.

What's the gripe? Would you prefer farm parties form, go in, see the message, everyone gets pissed at whoever the potential 'leecher' is that lied their way in, and then disband?

This obviously wouldn't affect learning parties, which form and sometimes actually succeed anyway.