I respect your choice and acknowledge that you've clearly done your research. I'm also not against veganism at all (if thats how I came across), I think most people would benefit from eating largely vegan diets but believe cutting out lean meats completely is unnecessarily restrictive.
However that statement is completely inaccurate, to say plant based proteins are 'healthier' is just false, health is entirely subjective and depends entirely on what aspect of nutrition you compare, there's plenty of evidence both ways and can consider everything from fat content, amino acids, pesticides, hormones, impact of insulin, bioavailability...etc, to just say plant protein is healthier is a bit misleading.
And there is little evidence to say vegan diets 'increase athletic performance'. The overwhelming majority of the worlds top athletes are omnivorous, they have access to the best trainers, nutritionists and scientists in the world. Margins in professional sport are so tight do you not think if there was anything they could do to gain a slight advantage then they'd do it? There simply isn't any convincing evidence to suggest veganism increases performance, when there is I expect to see far more vegan athletes. Granted there are a few vegan athletes at the top level but most of these made the majority of their muscular and endurance gains on omnivorous diets before turning vegan later in life and very few are the best at what they do.