Sent my complaint about this BS via their website email form Why restrict the hassle they are getting to Twitter?!
Should others wish to do same: tampax.co.uk/en-gb/contact-us
I went along these lines - feel free to edit and recycle this if you want to send your own complaint:
Biological sex is a fact of life. I understand there are those who are troubled by it, but there are other ways of supporting them without erasing women or declaring 'women' to be a controversial word.
I urge you to find a different way to reach people who do not believe they are women but who have periods. Please do not join this sexist trend of trying to make woman, women and girls into dirty words.
We've barely managed to get over the taboo of mentioning periods and menstruation - we do NOT need this backwards step whereby woman becomes the word no one dares to say.