Anyone ever just get seriously discouraged about peoples view on how easy/difficult it is to code?

A client has requested that they want a system built so they can create surveys and send them to people via email all in one tool. Im not a good front end designer but I know how to develop it. So they hired a designer to send me screen mockups and I will develop them. Easy enough.

This is where the bullshit starts... The designer was supposed to send me the V1 designs last Friday so I could begin building. I told them that I could have a rough version of some pages (with placeholder text and whatnot) ready for the following Friday (tomorrow). However the designer didn't send me the designs until 5 minutes before we were all meeting yesterday. We were all going over the designs in the meeting and this is how the conversation went (roughly):

Client: Wow these designs are amazing, I cant wait to see what it looks like when it functions. Are we still going to have a demo version by Friday?

Me: Well seeing as I just got the designs today, Ill have to look them over and get back to you on a new timeline.

Designer: Yah sorry about the delay, designing can be tricky sometimes.

Client: No worries, I understand. However I want to stick to the same timeline and have the demo by Friday.

Me: Well as I said, Im only getting the designs now, this is the first time I'm seeing them so I'll have to look them over and re-evaluate.

Client: Yeah but the designs are done so it will be easy for you to code it by then. It's all right there in front of you. I need to run, excited for Friday! Bye!

Designer: Bye!

Me: ...........

-- I know its partially my fault for saying I could have a demo done by Friday assuming the designer would have it done on time but COME ON. I hate when people say something is easy when they have no idea what it entails or how to even do it.