YABU I'm afraid. I suspect your friend has been dropping jokey hints and is now getting a bit more up front about it.
Soft play places are never going to be peaceful and obviously children need to let off steam, but screaming and screeching really are very unpleasant and not at all necessary. I sometimes go to a massive soft play centre and sit and do some work on my laptop while DS1 runs about. I can work quite happily through the normal noise, even when it is very busy, but I cannot concentrate if there is a child screaming - it is even difficult to hold a conversation through high-pitched screaming. It is a particularly penetrating noise and most people will dislike it, even if they don't say so openly.
Some children, particularly younger ones or those with any degree of sensory issues, may also find it unbearable.
It is something you can deal with fairly easily. None of the DCs in our family have ever been allowed to scream and squeal without being pulled up on it - mainly because it was the one thing that their great-grandfather could not stand in his own children so the grandparents generation didn't allow their own children to do it, and now those children pull their children up on it. My DS's cousins went through a stage of screaming, and DS1 would join in when he was with them, and we all stopped it as soon as it started and they very rarely do it now. A simple "Hey, no screaming!" tends to do the trick.
We are now very glad we did take this approach as great-grandfather is almost blind and has developed acute hearing so what was once just a dislike is now something that genuinely causes him discomfort. We wouldn't be able to visit them for any length of time if either of ours screamed regularly.
Just because soft play is a place for children to let off steam doesn't mean that they have to be allowed to make any degree of noise they want. Presumably you would be unhappy if a child came and stood next to you and screamed unceasingly? People have different tolerances and it is sociable to try and keep a lid on things that most people dislike to some extent.