I do not think you offended anyone. You introduced your post that you are simply not familiar with mikva usage by men, hence your view regarding it. And rationally speaking coming from that vantage point, you are correct.
In periods of time where tumah v'tahara was a halchic concern (i.e. when korbanos were brought, one was required to go to the mikva after experiencing a seminal discharge - whether through marital relations, wet dream, or other cause). Although practical halacha is lenient with a man being required to use a mikva after a seminal discharge nowadays, there have always been many who continued the practice of immersing in a mikva prior to Torah study or Prayer - some actually being of the opinion that this is a requirement. In addition, in Chassidic communities it became the norm to use the mikva every day as a means of purifying oneself before beginning a day of avodas Hashem. In addition, once a person has reached the age of puberty, there are oftentimes traces of semen in the urine - which means that technically one may "need" to use the mikva without even realizing that he had a discharge of sorts - which is one of the reasons given for people immersing before entering the Bais HaMikdash, despite not really "needing" to.
A mikva is definitely a place where predators (or just plain curious young bochurim) would like to hang around. In chassidic camps, a magid shiur or mashgiach is usually present (dressed) during the hours that the boys go before shachris, or on erev Shabbos afternoon. Most normal communities have set up systems to prevent anything inappropriate, however as was written a few times, one should never allow a child/young bochur into the mikva by himself. In addition as was written before, most mikvaos are not relaxed shmuzing men's clubs. Are there some that may unfortunately lack in tznius? Probably - so just don't go there.