What we do know for sure is that these allegations exist, he was transferred out of St. Marys to an all boys boarding school, and that his mannerisms are effeminate.
If I had a son at La Salette Academy I would be very concerned.
So, I don't know this priest, so in order to evaluate your allegations here, I went to watch the interview, and I declare this post of yours to be nothing short of slander and calumny.
He's not at all overtly "effeminate". While that doesn't preclude various proclivities contrary to nature, this characterization of him is slanderous. Just because he's slightly-built, doesn't speak in a bass voice (though it's not super high or soft either), that does notmake his mannerisms "effeminate". He comes across, rather, as more "nerdy" (perhaps, and I hesitate to use that term, since it's also somewhat uncharitable, but in the interests of defending him against this smear of yours) ... and noticeably very "fidgety", like he's somewhat nervous and high-strung (which could explain Niles' characterization of his being extremely nervous in the police interview). Most people would be nervious under thoes circuмstances, but I can see Father here having his "baseline" tendency to already be high-strung and fidgety amplified by the stress of such a situation.
He also comes across as very bright and articulate, absolutely nothing like how he came across in his text, and then mentions how his assignments since his ordination have entailed working with the youth ... so putting those two together, it makes it all the more likely that he was deliberately just trying to sound "cool" in the text messages. It's the same thing I mentioned with the other priest, where his natural mode of speaking and expression with adults was completely different than what I witneesed when he was among some teenagers, and that's a clear indication that he's "trying" to act that way.
Finally, as I already pointed out, the contradiction (in 99% of all cases) betewen his being "interested" in predating upon boys vs. being "interested" in predating upon girls. It's rarely both, but nearly always one OR the other, and trying to smear him as both smacks of total lack of charity.
Now, one should be careful not to leave children alone with ANY priest, since not every sodomite shows open signs of effeminacy, and some of the non-effeminate ones actually despise the effeminate "lissthping" limp-wristed ones. You never know really, and many have been fooled by some priest who appeared to be pious and devout, etc. Some of the priests end up having many of the laity they served defend them tooth and nail because no one could believe that such a "holy priest" could have done such at thing. You can't go on appeareances. But I reject your slander that Father Kopec has "effeminate mannerisms". I've seen all kinds of men with somewhat "softer", less aggressive, demeanors being accused of being "effeminate" ... knowing the charges to be pure calumny. They're usually hurled by individuals who consider themselves (in their ego) to be extremely "macho" ... when in most cases they're not and just projecting their own wishful thinking.
I also believe that every post like this above that is made by an "Anonymous" should be deleted, whether it's about sɛҳuąƖ matters or not, such as the one Anonymous buffoon who came on here slandering another SSPX priest by name without giving any evidence or details.
Engaging in this behavior could constitute grave sin for calumny and slander.