But of course, had a lawyer from some other country- say Saudi Arabia- offered damaging information on Trump to Hillary Clinton's campaign, there's no way they would've taken the meeting. lol

The correct thing to do, both politically and legally, is to take the meeting and obtain the information. Once you have it you can take it to the police if there's evidence of illegality, or if its evidence in an ongoing case. Or, you may or may not decide to use it against your opponent. To refuse to meet would be a dereliction of one's civic and political duty.