Is anal intercourse dangerous or damaging? It surely sounds dangerous!

Some risks. There are risks w anal sex. Having anal receptive sex can lead to transmission of sexually transmitted diseases. Repeated anal sex may loosen/ weaken the anal sphincter affecting fecal continence. The anal/rectal mucosa is not well protected which makes it susceptible to tearing w penile penetration.
Anal Sex. The simple and best answer is no. If done correctly this common sexual activity can enhance the sexual life of couples. Many men and women participate in this type of sexual activity in most cultures of the world. Yes, there are some risks to this activity. But, if done gently and with care it can be very much enjoyable. I always recommend a guide book to start to learn technique.
Shouldn't be. If done carefully between consenting adults. You need lots of water soluble lubrication plus slow insertion with partner relaxing their anal sphincter. Diameter of most penises is less than diameter of very large bowel movements, so anus is large enough to accommodate. I repeat, only try it if both partners want to, and stop trying if it feels too unpleasant.