If a clerk hates something enough to discourage consumers from buying it, they would find anything to do so. So, yeah, that will happen in extreme cases, but it would happen with or without the slower clock speed.
You know what else will happen?
Customer: Hi, I would like a Wii U.
Gamestop Employee: Are you sure?
**Bullshit Bullshit Bullshit**.
Customer: Okay, well, then... can I get Mario on Playstation?
Gamestop Employee: Wh- No... that's only on the Wii U...
Customer: Great, then shut the **** up and get me a Wii U.
Anyone can point to these very specific scenarios. How often are either to happen that way? The people who want a Wii U are going to get a Wii U. The uninformed are probably getting it for someone else. The people who don't want it couldn't be convinced anyway. Are we making mountains out of mole hills? Ehh, probably.