I really hate this idea in activist communities that everyone is under an obligation to be nice to others. It seems that, if a so-called ‘ally’ fucks up, you can’t call them out on it. Or if you do call them out on it, you have to couch it in pretty words and apologies.
Privileged people (cis people, men, white people, currently-able people, neurotypical people, etc) who want to be allies need to learn to back the fuck off and take a back seat occasionally. They need to learn that, though the rest of the world treats them as default, in these spaces their voices are not and should not be the most important voices, and that they should let marginalised people speak for themselves about their experiences.
The thing is, many marginalised people have been through too much to expend energy being nice to people with their foot on our necks. Sometimes they shout, they swear, they come across as nasty – because they deal with this shit day in, day out, with no reprieve. Cut them a little slack and let them be righteously angry.
Not everyone in a marginalised community is going to be nice, and those who want to be allies can’t expect us all to roll over and be nice. Sometimes a cis person (or man, or abled person)’s bullshit is the straw that broke the camel’s back and a good ally, upon being reprimanded abrasively, will realise that and pull up their grown-up panties and move on.