I don't know where the WD-40 haters get their info or experiences, but if you perceive it to be the problem, you are using it improperly, or expecting it to do things it's not intended to do, like long term lube. It is totally harmless to sewing machines and components. It is a solvent and hygroscopic.
It has the ability to soften varnishes leftover from dried lubricants. With some heat the capillary action will pull it into components that are siezed due to dried lubes, and frees them up much quicker than any other aerosol. After the parts are totally freed and flushed you add your favorite SM lube. I'm betting you weren't thorough in your clean up, or neglected to lube after use.
WD-40 has many uses and is not harmful to sewing machine finishes. In fact, back in the day before specialty products, show cars were given a quick wipe with WD-40 for bringing up the shine. It's also used as a great bug and road tar remover. Has been for years with no harmful side effects.
It's also an excellent water displacer, and is used in many industries to absorb moisture and prevent rust.
I have no stock in the WD-40 corporation. The only money I've made off it is the benefits it provide in the workplace. I've been using it pretty much from the time of it's inception.
OurWorkbench- Your experiences may not have been good, but it was a user problem. So... since your are regarded as the "mechanic" around here you have a lot of influence on others views. Don't ruin their experience just because you don't know what you're doing.