“actually enables employers to fire for no reason? If anyone knows the answer to this, please let me”

Union supports like to say that with out them, people can be fired with out cause.
The real meaning behind that statement is the belief that the Union will stand up for there members.

Truth is, it may be a little harder to let go a Union member than a Non-Union Member, but it also may be easier, I have seen Unions try and roll members out who they believed to not be blind supporters, the Union is also basically a for profit business, and there for often resistance to actually standing up for its members, that cost money and time and the Union would prefer to spend both in increasing cash flow instead of actually defending members rights.

Also, An Employer dose not really want to fire people, that is expensive and finding new people and training them cost a lot.
If one is honest and hard working most businesses will try and keep people even in hard time by moving them to other departs if need be.

I have had both Union Jobs and Non-Union Jobs, I have found it is better to put your trust in yourself as far as keeping a Job rather than in the Union, who I found will stab you in the back for a buck.

So the Answer is, there is No correlation between Right to Work and Job Security, but Union Supporters like to Imagine one.
Union supporters have a vision of employers half mad like some charituer from a B movie.
In reality, that Boss would not last long (I actually had one of those, 2 months after she fired me, her boss Fired her. He was growing tied of losing so many fine employees. – so you see, it self corrects for its self, and the Union really makes No diffrance)