[LarryA]

ohhh, I just looked up the font, that is a challenge...

Don't call it a design issue, call it a technical or usability issue, show "technically" this font would not be good, see how it relates to menus, accents, etc. Illustrate the problems with menus, etc. and how you would have to have custom code for all this, in comparison to a non italic font.

A mock up helps, generate a comparison with standard fonts at real-world resolutions.

Thirdly, you should try to share their enthusiasm, grab some of their other materials and see what their standard designs have to offer that you could implement, then approach them and say "you know if I implemented this alternate font, color scheme, theme, or logo we could create an effect that better ties this into your business."