This is a major fallacy behind those who push the conspiracy theory: they deny the right for DS9 to have any similarities, even when those can be proven to have long roots. Moreover, it shows that this is really a turf war. DS9 can't have a station, can't have ships, can't have other races, can't have women officers, can't fight, can't explore religion, can't keep coming back to the same stories, ... .
Long roots? What utter nonsense. Ro Laren was introduced a month before B5 was publicly announced. As far as I know she's the first Bajoran character and the first ground work for DS9. So your long roots are introduced during or after the finalization of JMS's deal with WB.
Let me make a few things clear.
JMS was trying to get B5 picked up for years, including Paramount, they apparently had multiple positive meetings but suddenly stopped.
B5 was picked by WB and announced in Nov 1991.
Ro Laren, the first real tie into DS9 was introduced Oct 1991. DS9 itself went into production in 1992.
The biggest point is though, DS9 came out January 1993, and the B5 pilot came out in February 1993. B5's season 1 also came out a year later in January 1994. The timing means that any weird similarities between the two shows would likely have only derived from the pitch. Unless there was some article or trailer about b5 that paramount saw and looked at.
So what did they have in common, based on Emissary:
1. A "changeling"
2. The wormhole/jumpgate
3. The religiously oppressed race and the oppressors
4. Diplomatic aim of the station (Sisko was ordered by Picard to get Bajor ready for federation membership)
5. The haunted commander who survived a massacre
6. The multi-species, transit hub nature of the station
7. Angel-like aliens
8. The station situated in neutral space
9. The darker tone
10. The prejudiced, female XO (according to the B5 pitch bible)
Now maybe you can say like, 4, 6, 8 are coincides. But the rest? Pretty doubtful. And if they took ANYTHING from the B5 pitch, then EVERYTHING is suspect because it means they actually looked at it when developing the show.
And yeah I know people have already said that TNG already had wormholes. But those weren't permanent features on a show were they? DS9, from a franchise about warp travel, just decides to adopt a permanent other means of transportation that coincidentally is just like B5?