In order to prepare for this conversation with your client, make a list of different factors and aspects that could come up. As always, no single opinion is correct, it always depends on the client and we are "reality waiters" - meaning that the client can listen to our offered perspectives and ideas, but it is up to the client to decide and choose which reality or truth he/she wants to accept.
It might help to talk to your family or friends about this, to get a feel for the different views and arguments. Keep also in mind that changing an opinion is valid.