I dig this motto and poster. I really do. Actually, I sort of love it, the same way I love Westminster Abbey, fascinators, and British sangfroid.
It's been co-opted by every social media DIY lad or lass who fancies themselves clever. Pinterest is lousy with eye-rollingly-cute variations on the original theme: Keep calm and craft on. Keep calm and call your mom. Keep calm and have a cupcake. Keep calm and go back to December (yes, there is a whole line for Taylor Swift fans). I can almost get behind "Keep calm and STFU." Almost.
Do most people even know (or care) that this was originally created by the British government to keep up morale during World War II? I suspect most people think a graphic designer banged it out to sell on etsy. Stop decorating your Crate & Barreled-out entryway and breakfast nook with knockoffs that speak to your hobbies and sensibilities. Keep the ubiquitous original if you must (I know you paid a pretty penny for that silicone iPhone case) but carry the rest of these designer imposters straight to the recycling bin, where their recycled arses belong.