If you publicly state your (real) age or other physical identities, you are and will encounter discrimination. However, if you are anonymous then other users do not have any physical identity to judge you against, except for what you write online, so they don't know whether you are really a child, so you cannot be discriminated against your age, a female, so sexist idiots can't write misogynistic insults against you etc.
People are often afraid of stating their views on a subject, especially when it doesn't flow with the current. That's where anonymity comes in. Anonymity allows those people who are too afraid to voice their views on something to do so. If people have the option of sharing their thoughts without being recognized by anyone, then they will most likely express their opinion on a certain regard. Therefore, anonymity gives way for the flow and exchange of thoughts and ideas.
However, with anonymity does come the issue of cyber-bullying. Nevertheless, just because a few people decide to abuse the privilege of being able to post whatever they want on the net without suffering the repercussions does not mean that anonymity should not be allowed. That's like saying that there are some racist people in the world who don't like people with dark skin, so now all of those people with dark skin should be erased from the face of this earth! (On a side note, I am not supporting racism with this statement, I am merely drawing an anology to make my point clearer.) Cyber-bullying is an entirely different topic, and for that, we need to erase this mindset from people that their actions won't have any repercussions.
All things have pros and cons, so we can't simply say that anonymity is entirely beneficial, not can we claim that it only brings negativity in our lives. But, in my opinion, anonymity does have more pros than cons, due to which I wholeheartedly believe anonymity should not be advocated against.
Anonymity allows people to release their opinions free without any consuquences. And that could help in politics or just simply everywhere else where people might be scared of the backlash that they may recieve just for stating their opinions. Thats a reason i simply believe that anonymity should be a human right.
Anonymity, especially amongst large groups, can cause what is caused deindividuation. This is where individuals become less about themselves, and start becoming more a part of a group. This is what we witness in mobs - people lose themselves and often lose the accountability that comes with acting as an individual. So in fact, anonymity can actually have the opposite effect of letting people realise their own opinions - they are more likely to agree with the opinions of the group majority than think for themselves. Certainly it is important for people to have the right to say their opinions without fear, but anonymity is not the answer. This is where we get internet bullying - trolls hiding behind a key board.