I agree that euphemistic language does not take the act seriously enough, yet I feel "sexual assault" is too strong a choice for this specific case.
It fits the legal definition - both in the UK where that article is from and for the US Department of Justice:
Sexual assault is any type of sexual contact or behavior that occurs without the explicit consent of the recipient. Falling under the definition of sexual assault are sexual activities as forced sexual intercourse, forcible sodomy, child molestation, incest, fondling, and attempted rape.
(bolding mine)
From a legal perspective, the word "
assault" does not automatically indicate actual or threatened violence. It means: "Intentionally putting another person in reasonable apprehension of an imminent harmful or
offensive contact." (bolding mine)
What the DJ did to Taylor Swift was, in fact and in the law, sexual assault and it should be called as such. Using euphemisms or substitute words imply that it is not a sexual assault, and leave the victim feeling like she (or he) are over-reacting when they object.