Something I read online

"So what languages do you speak?"
"Chinese, Swahili, Czech, and Hindi. And enough Maasai and Romani to get by."

Sounds great to me! 

Speak more than one language? This is what it does to your brain

Which languages should one learn?

 The languages you have most use of. The languages you want to learn.

Now, if you want to learn most useful languages, in general...

America is a pretty easy thing, being rather monolingual. You can communicate with almost all, if you speak Spanish, English, French and Portuguese.

To communicate with Africans, add Arabic to the list. These five languages get you through most of Africa.

To communicate with Europeans... most Europeans today manage in English, but it helps if you add Russian and German to your list.

To communicate with Asians... again, most Asians speak English as well (modern, urban Asians at least), but if you add Chinese to your 8 languages, that covers a lot more. Add Hindi/Urdu and Malay to the list, and you cover some more ground.

- English
- Spanish
- French
- Portuguese
- Arabic
- Chinese
- Russian
- German
- Hindi/Urdu
- Malay

Esperanto

Why Donovan Nagel won't learn Esperanto?

Basically, because he believes studying Esperanto makes you a religious fanatic and a leftie.

I could have just passed by that, but he said something that triggered me.

"Now, I know this will probably stir up a beehive (I wish I could say I’m sorry but facts don’t care about hurt feelings)"

Your subjective opinions are not facts, Donovan. You could say you're sorry for expressing your opinion in a prejudiced and judgmental manner - because that's what you are doing - but in reality it's you who doesn't care about hurt feelings. You just call yourself "facts" because you are a pompous ass.
(Also, it doesn't stir up anything, because no-one cares about your opinion that much.)

Now, I don't much care about learning Esperanto, because it's boring and uninteresting and pretty unoriginal, and my reason to study languages is not to be able to communicate with people. I think I have enough languages already to not to try to get in a quickie to make it speedier to learn more languages, but I might learn it just because it is a quickie. Also, because my father knew it. 

So, without further ado,

"Esperanto has always been a means to a political end"

Bull.
I know that languages are carriers of mindset and ways of seeing the world. But Esperanto? No. Simply because it is a conlang.  

"Esperantistan is an ideologically homogenous landscape"

Bull. It's a way of communicating, and nothing else.

"Not only does it have no culture but its adherents are delusional"

There are many different definitions to culture, but as he says, Esperanto doesn't have a culture attached to it, which means that one doesn't need to waste time with acculturation when learning it. No "half third times twenty" or "ten seven" here.

"Esperanto evangelists aren’t just passionate – they’re fanatical"

I'm sure there are some fanatical Arabic lovers as well. 

"It might help you learn other languages but at the expense of time best spent on the language most important to you"

Well... of course you should spend time learning languages you want to learn, but if you learn languages to learn languages and to communicate with people, and knowing a language - any language - helps you to learn another languages easier, then you should learn the language that is easiest to learn, and Esperanto is one of those languages. It also comes without the cultural baggage, which makes it even easier to learn. No idioms. No culturally sensitive words. No complex courtesy phrases. Etc. It's just pure language, easy peasy. It doesn't take long, and if you know it, you will be able to communicate with a lot of people. So, you won't be "wasting" much time, if you decide to learn Esperanto.

"Esperanto has failed – not that we needed it anyway"

There has always been lingua francas, and these languages have been national languages, which have made them not suitable to be used as lingua franca, because if two nations are at war, they wouldn't want to use each other's language. During the WWII one could get into trouble just by knowing German or Russian. (Now, people got into trouble speaking Esperanto as well, but ah - what didn't they get into trouble for, really...) There was a need. Otherwise Esperanto wouldn't have existed. Duh.

Of course a living language is always more successful than a dead or constructed language, but has Esperanto failed? There's 2 million Esperanto speakers in the world. There's probably a couple thousand Native speakers of Esperanto. Generations of native Esperanto speakers.
Esperanto is a very young language. It's only 133 years old. English is about 10 times older, with even longer history in pre-modern forms. What will Esperanto be in 1000 years? 

"We’re rapidly losing endangered languages and more than half of them will be lost forever by the end of this century."

Now, this is the only reason I can accept as valid - learn an endangered language rather than a conlang. But he isn't saying this as a reason not to learn Esperanto. And he chose to learn Arabic... As far as I know, he hasn't studied one endangered language. He says he's interested in studying them, but - I am interested in everything between the core of the planet to the deepest space millions of light-years away, and it doesn't mean anything. Not one language was saved by interest alone. So, who is he to bash Esperanto learners for choosing to study that and not an Australian language?