I was actually thinking more along the lines of personal vitriolic comments towards players rather than general booing of a team - obviously the racist, homophobic, etc comments are already illegal. But who knows how individual players react to what is deemed banter and what they're own perception of that is ( it is their workplace). It'll only take 1 player, or manager, to change the landscape.
I think players would hear worse from their counterparts rather than the crowd. Even if not, I think most players drown out crowd banter/noises.
Of course, there are exceptions. Eric Cantona comes to mind, but then again, his mother had just been called a 'French whore' according to reports. And he took matters into his own hands, and feet to be precise.
The abuser, a "Palace supporter Matthew Simmons, who had run down 11 rows of stairs to confront and shout abuse at Cantona. Simmons was alleged to have used the words "**** off back to France, you French bastard"." (according to Wikipedia) and copped a penalty too, "The fan that Cantona kicked, Simmons, went on trial separately where he claimed that he only shouted "Off! Off! Off! It's an early bath for you, Mr Cantona!", but was found guilty of abusive behavior and handed a £500 fine and banned from the stadium for a year. Immediately after the verdict was proclaimed, Simmons then assaulted prosecutor Jeffrey McCann for which he was sentenced to a week in jail plus an additional £500 fine as well as £200 in legal costs." Irony, Karma, whatever, as if you'd run down 11 rows of stairs to call out, "Off! Off! Off! It's an early bath for you, Mr Cantona!".
Oh, how utterly demure of Mr. Simmons. Yeah, right. The Judge saw straight through that one.
Sure, not exactly to what you're alluding, but I doubt any court would rule against mere banter from the crowd. It'd have to be very offensive to get a judge to rule in the plaintiff's favour, just as in the Simmons' trial. And that was almost 30 years ago. Nowadays, the word '****' is bandied about like it was part of a Shakespearean sonnet.
Besides, players should know that they're going to cop some abuse from the spectators and as long as it's not "racist, homophobic, etc." then that is where it will end, imho.