The example is not really offensive (in my opinion) but slang. It's in the rule because that sentence (Des petites bites) was found to cause a false alarms in the rule ACCORD_NOM_VERB. The false alarm was fixed and the example was added to test that it was fixed. The false alarm happened because "bites" is also a flexion of the verb "biter" (slang for understand). It was fixed here: https://github.com/languagetool-org/languagetool/commit/b764ea458caf6a596633bdc48545dfa8f66fba79 Anyway, that example is not very important for the rule ACCORD_NOM_VERBE so I've just removed it, if that makes someone happier.
No. The technical word you refer to is spelled differently: bitte. The 2 words "bitte" (= bollard, a relatively rare word, not offensive a all) and "bite" (= dick, also flection of slang word "biter" =understand) are pronounced the same. They are homophones. There is in fact a LanguageTool rule "BITTE_BITE" to detect the confusion. In that rule, you may find examples that are slang (not offensive), but it's precisely the goal of the rule to detect the awkward confusion, so I think that the examples are legitimate to test the rule BITTE_BITE. In any case, keep in mind that examples are not shown to users, they are only there to test rules. Examples are only visible to those who wish to contribute to improving rules. Only messages are shown to users.
Actually the first two or so are shown to the user in the stand-alone version when they select "More..." on the error. All examples are also shown on community.languagetool.org (which mostly addresses developers or people interested in the rules, so it makes sense to show them there).