It's not toxic masculinity to view large male genitals as more masculine. Sure, it's sexist small-minded heteronormative bullshit, but it's not toxic masculinity.

(Toxic masculinity as generally used refers to ideas about how men or boys should behave which are not compatible with either a healthy society or an individual's mental health. )

(There's some variance on this where it shares some overlap with "hyper masculine" folks who have unusual presentations of characteristics usually caused by the male sex hormone, but I believe smaller genitals are also a potential consequence of excess steroids or testosterone.)