Care to offer an explanation why?
Ref counting is not superior or inferior to explicit, restrictive ownership semantics. Those are simply different trade-offs.
Nim might be strictly inferior for writing a heavily multi-threaded web browser because of its memory management approach but that does not mean the approach is generally inferior.
Seems to me that Nim aims to be a "casual", rapid development / friendly (Python-like) language. Ownership semantics like in Rust do not fit there.
For different use cases Rust-style ownership semantics (when the performance of GC and runtime interoperability become an issue), or Azul-style pauseless GC (when you're willing to trade throughput for latency), or shared-nothing architectures (when you need them for legacy reasons like JavaScript, or want a simple programming model like Erlang) can work great.
It's a price that a lot of people are willing to pay, because of how badly they want what they're paying for.
Nim and Rust have different goals, different tradeoffs, and overlapping target audiences. Having both is good. Making them fight is bad.
Since it's 2015, it seems fair to point out when a new language offers something neat, but in a way that isn't safe.
With regards to memory safety, it is not. https://news.ycombinator.com/item?id=9050999 is an old comment from Patrick, but in today's Nim, it segfaults in both release and development modes for me. Rust's guaranteed memory safety means that Rust code (without explicit unsafe, the vast vast majority of code) cannot segfault.
> I don't understand why people think that Nim is "terribly unsafe" when in reality it's like any other language
For example, unless I write a bad cext, I cannot get Ruby to segfault.
None of this makes Nim a bad language. All languages have tradeoffs.
That is factually false.
"Perhaps it's not as safe as Rust"
And there even you have contradicted yourself.
"Perhaps it's not as safe as Rust but that brings specific trade offs most people dont wan't to deal with."
That much is true ... and can be said without telling falsehoods, like your first statement.
"I don't understand why people think that Nim is "terribly unsafe" when in reality it's like any other language"
You are confused by your own strawman.
All languages have faults. Engage with your critics, own your faults, and either correct them or justify them based on your principles.
EDIT: To give an example, pcwalton also initially criticized Go for not being memory-safe for values of GOMAXPROCS greater than 1. However, the Go team later implemented the dynamic race detector, which, if you've followed pcwalton's comments at all, you know that he is actually quite impressed with.
(I suppose, in the future, pcwalton should just generate a throwaway before commenting on Nim.)