I never disagree with a client. Even if I internally feel it won't work in reality, I always start my response with "That's an excellent idea you proposed, let me try if it works and get back to you". I come back after a day or two as to why the proposal won't work (if it was a bad idea to begin with) with sufficient data. Client is happy you that you considered his proposal and you've avoided a potential standoff th…
Interesting. We usually say that a good consultant should be senior enough to stand up to the customer and at least be able to inquire the basis for something. And also disagree when the customer is clearly wrong. But your way of doing it clearly removes the initial head-on. One could always reason about things. But to promise to investigate (and then deliver) looks (and is) professional. But I will never say yes whe…
Client: "Encrypt our data using the md5 cipher."
Consultant: "I will investigate the feasibility of this."
... two days pass ...
Consultant: "I have considered your proposal. I believe we should encrypt your data with SHA-256. md5 is insecure, here's several references. SHA-256 is much more secure and more popular. It is a NIST standard, and just as cheap."
Client: (probably) "OK, if it costs the same and is more secure, sounds good to us."