I don't think that a President at a joint press conference after a summit should publicly attack the other participant.
Foreign apology tour? Not hardly. Just ask the NATO folks. Trump made several tactical errors. He should have had Pompeo in the meeting with Putin. Trump thinks he's a great communicator and he's not. He's inarticulate and should have told the reporter that the question was inappropriate. It was, and it was a setup. His own hubris landed him in hot water.
I think the question was entirely appropriate and in fact, inevitable, but I don’t think he needed to “attack the other participant†to avoid throwing his own Intelligence and National Security Community under the bus. I think good staff work would have had a statement like the following ready for the President to say at the Press Conference when he was (inevitably) asked about Putin and Russian meddling:
“I have been and will continue to hold Russia accountable for meddling in past and future US elections. Although President Putin has denied the meddling, Dan Coats and the rest of the Intelligence and National Security Community have provided me with the evidence of their involvement. Further, 26 Russians have been indicted by our Department of Justice. Regardless of these facts, I believe we can both hold Russia accountable along with improving relations with them all at the same time. That is the challenge before us, and I believe, we together, are up to the task.â€