French is such a misogynistic language...
You could have a hundred people, 999 women, one man, you're still gonna have to use 'ils', which is the masculine version of 'they'. It takes one fucking man to change everything to the masculine. You may have millions of women, if one man is in this group, you're gonna have to refer to the group as 'ils' and not 'elles'. And you know what, French are screaming it's deconstructing the language when people are saying it should change.
Words are powerful. Words are what win someone's heart over. Words are used every day. Some hurt, some make you feel better.
I'm pretty sure it won't hurt the guy's masculinity to be called 'elles'. It's not gonna turn him into a woman. It's not gonna make him wear a dress or have a higher pitched voice or turn him gay or whatever the hell people are afraid of. It's not gonna make him a bad person. Do you see women wearing male clothes walking in the streets? Do they have a deeper voice? No. But they've been called male more than a thousand times already.
You are ignoring human beings when you don't want to call a group of women 'elles' simply because a man is among them.