I totally agree with this. It feels utterly uncivilised. If you don't like a certain player or the opposing team, then just politely shut up. Fans should be focusing on cheering and supporting their own team and just leave the opposition alone. The stupid thing about bullying the opposition is:
a/ It's bullying. Are these fans grown adults? What example are they setting for children? Would we accept this kind of behaviour from children at a kids' match? If not, why is it acceptable for adults to do this at the professional level. And bullying shouldn't be tolerated in any form, verbal, psychological, physical etc. There is just no place for it in society.
b/ It's
unsportsmanlike. You hate the opposition? Guess what? There would be NO game without the opposition!

You
need an opposing side in order to have a match! Good luck playing one without it.

Again, I think it's important that adults also role model good sportsmanlike behaviour and spirit to children.
Aren't these games meant to be family-friendly events?

Because if adults are allowed to cavort around like immature thugs, then how does that create a family-friendly atmosphere? I attended a football (A-League) match years ago and saw adults
swearing despite the fact that there were
c h i l d r e n in the audience.

I ended up reporting them to staff.
Could you imagine this happening outside of football codes?
e.g.
* Other sports like tennis, golf or surfing etc.
* Other forms of non-sport fandom. There can be some mischievous faux-animosity at these events; e.g. when I saw the premiere of Star Wars III Revenge of the Sith, there was a dude who came along to the line wearing a Starfleet uniform, and walked up and down giving us the Vulcan Salute. People booed him and eventually a bunch of people dressed as Jedi & Sith chased him and playfully beat him up with toy light sabres. But it was all done as a spontaneous joke, there was no
real harm done -- and quite frankly, this was a midnight premiere, so there were only adults there anyway.

But could you imagine if, when Star Wars Episode VII comes out, if Trek fans came along and started hurling verbal abuse? Or if Marvel fans came along to screenings of Dawn of Justice and started abusing DC fans? Or if DC fans came along and abused Marvel fans at Ant-Man?
WHO DOES THAT?!? 
And if they did, we'd consider them to be complete idiots and utterly
condemn that behaviour.
If we as a society cannot even tolerate other people's differences in supporting different sports teams, how can we be expected to tolerate other differences such as culture, values, religion, sexual preference etc.??

Intolerance is just ugly in any form.
Come to sports events to cheer, not jeer.
My 2c.
