I am so glad my DH is on the same page with me about the cake smashing thing being ridiculous. As far as we're concerned, the most so-called "romantic" day of your life, just hours after taking lifelong vows of honoring and respecting one another, in front of each others' nearest and dearest, dressed in your finest and often with the bride having spent a good deal of time and/or money on her hair and make-up is simply NOT the time to do something as childish as push chunks of cake into each others' faces.
That being said, if I were to attend a wedding where it happened, I would never voice my opinion to the bride and groom. To each their own. Even in a situation where I KNEW for a fact that one of the members of the couple didn't want it to happen, it's still not for me to comment. But I can think whatever I want, and I can't promise that I wouldn't think less of that half.