In Tanach, there are words that operate as male or female. The most famous is דרך , as anyone who studied the beginning of masechet kiddushin knows. Others are ארץ, קצה, יתד,דוב , and many others.
There are essentially three dialects that we deal with, each with its own rules and quirks. One is Lashon Tanachi, second is Lashon Chachamim-Chazal (mishna, gemara, siddur and machzor) and the third is Vernacular-Modern Hebrew (עברית מדוברת). Of course there are subgroups and sub-sub groups.
In spoken Hebrew, the plural of טלית is טליתות. So declared the אקדמיה ללשון. Proofs from Chazal are not proofs, they are just לשון חז”ל. Notice that Chazal replaced the Tanachic ש (sin) with a ס ( samech). Why? It served their purposes. Right or wrong? Inappropriate and irrelevant question. They did it because they wanted to.
In any case, it is foolish to make fun or denigrate anyone who utilizes vernacular instead of sticking to the rules. The rules are not always operable, and different systems have different rules. I like rules, they help us understand each other. Breaking them may be annoying, but hardly a crime.