This happens all the time online, fashion changes constantly but bad taste will unfortunately always be in fashion although limiting the freedom to screw up a car however (which is ofcourse highly subjective and not limited to certain brands only) is missing the point by quite a margin.
I'd rather see not only what I'm up against but also who I'm up against and make, no doubt completely unfounded, judgements about their character and laugh at their dubious choices.
It's quite rare in fact to find a "soulmate", someone who hasn't put a hideous paint colour or inappropriate wheels on their cars and shares my taste for understated machinery.
But alas, that's GT-life I guess, although I hoped a game like GT would attract a more, ahem, "mature" crowd.
For example the Audi RS6 Avant, which to me is the ultimate Q-car (or sleeper as you Americans tend to call them), and pimping it out ruins the entire character in my opinion (I've seen someone with a bright orange one with a carbon hood and I believe gold wheels.....) but you should ofcourse be able to do that, hideous as it may be.
In fact, all these examples of bad taste make the objections some have for a livery editor strangely enough irrelevant.
It can't get any worse than some examples I've seen build with the limited amount of freedom there's now.
Think I even would prefer to see the entire back catalogue of a certain "actor" with the surname Jeremy displayed on the hood of an opponent's car (or any disturbing/offensive paintscheme) than witnessing some of the monstrosities produced right now with limited means.