At the Universal Congress of Esperanto
lrb.co.uk
lrb.co.uk
There is a book by Richardson I think (learning and using the international language) that has a lengthy introduction on why its a good idea. The language is really simple to learn and is generally easy to learn for speakers of the major language groups (Germanic, romance...etc). We waste millions of dollars on translators. Think of the UN where they have to translate complex ideas in real-time. There are numerous articles on how errors are frequently made. Think of the Soviet Union "we will bury" you really meaning we will outlast you. This also keeps us from infringing on other culture's local languages. Examples are Welsh people defacing street signs in English. Most Americans think it is dumb because we like having the rest of the world spend years to speak our own language. The tables will eventually turn.
In general, lab-bred languages are a 19th century concept (or early-20th if you prefer) of the "smarter-than-though" guy who thinks he'll unify the world from his university office and all that's lacking is a "common language" people will adopt en masse.
Especially attemps such as esperanto, in a time when linguistic understanding was totally lacking.
Actual languages are breed in an evolutionary fashion over centuries (or millenia in some cases), and are shaped to fit the culture and history of the population that breed them.
As for "universal languages" we had them too aplenty, and they are adopted for commercial, cultural and other reasons based on an initial push by a prevailing country (Greek, Latin, French ("the language of diplomacy" at some point), now English, etc).
Even the least succesful of those universal languages has had 1000x the reach of artificial languages like Esperanto.