In case you still do not see why this is okay, you may want to read a brief article from the Cato Institute describing how these current "bad" rules are relatively speaking, new.
We need to get the rules back to more like what they were.
Senate Rule History on Filibusters:
http://www.cato.org/pub_display.php?pub_id=3169
"Ronald D. Rotunda"? Looks like a pseudonym if I ever saw one! ;O)
Thanks for the link, CM. Excellent write-up. I've added it to my public links.