That's because Crusher would not kill after she mates. Janeway would.
Sorry but I don't see the link.
All I see is that Chakotay was far to be the good guy respectable to date when he boarded Voyager (himself confessed that he gave life to the rage he felt through violence, regardless he used it himself or by supporting others = from those who were under his command, I mean!) and even if he tried to redeem himself during the 7 years Voyager was in DQ, his behaviour left something to be desired from time to time, not only on a personal side, in playing it sometimes a bit too personal but, as First Officer too, in betraying shameless Janeway's confidence/leadership when she didn't share his opinion/his way of doing things (I remind that the practice of psychologic torture isn't forbidden and in any case, the using of physical violence is prohibited...although sometimes necessary when time is too short!) -> hey, he even thought to mutiny... even if his project came out of his head quickly; maybe because he perfectly knew that any attempt would be doomed to failure and not without risk/consequences for him, no matter all excuses he found to justify his decisions. Some were understandable while some others weren't).
BTW, I have a question, do you really think that when he led The Val Jean, his general behaviour and decisions taken were always morally acceptable?! I doubt it very much and nobody would have dared to tell him to stop before it was too late... if he even listened to them! In fact, he was too emotional to act logically and/or in following the book!
(-> I remind too that Voyager and her crew were lost in middle of nowhere in DQ, to face numerous ennemies and other danger, whatever on duty or on their free time. There was no room for doubt, for question and I would even say, for matter of conscience in this situation ... although producers/writers tried to infuse the idea that Janeway and Chakotay acted, at different personal levels, on their principles.
And to return to J/C, it was clear to me that after Scopion and still more after Equinox and Endgame, that Janeway couldn't rely on Chakotay's loyalty/respect and confidence. As for an eventual love interest for Chakotay, even if Janeway had shown herself sensitive to his flirtation in first 3 seasons (what was a mistake, if you want my opinion because it sent a wrong message), she told him "no" a first time at the end of "Resolutions" by distancing him physically after to have spent a month alone with him on an unknown planet and then, later in "Hunters", after to have spoken of her "Dear Jane" letter, she could not be clearer about her disinterest. Yes, she liked him but as a dear friend, nothing more. And she acted afterwards in this regard, in flirting with an alien named Krashykk then, in dating Michael Sullivan, a hologram and finally,after to have been released of her identity after to have lost her memory, she lived an intense relationship with Jaffen, an other alien.
-> If Chakotay continued to be hopeful after her polite rejections and love affairs,
it was he who was stupid!
On the other hand, we had Picard/Crusher's romance, which was almost natural and lovely to see/follow through years. Both were Starfleet in heart, they knew each other for awhilethis was why there was a certain familiarity in their behavior toward each other. They were always trustful and respectul on the Bridge as outside, always taking care not to mix the reality of their positions on board, with their consequences (actions and decisions) and their feelings for each other (what neither Janeway or Chakotay kenw how to do!).
(I always heard that a deep confidence, respect and loyalty were essential for a love story becomes serious and works (same for friendship) and when one of the two parties tends to show some weaknesses in these areas, perhaps it is wiser to consider a non-relationship and they stick to remain cordial towards each other and that's ok. Some people are made to be together for better and for worse, while some others should keep distance if they want to stay emotionally healthy/well-adjusted!
)
) and their dissensions never showed up on screen. Still more surprising, sometimes their acting gave even the impression that their characters flirted... Perhaps it was what we call here "de l'amour vache" (= though love)?! 
... contrarely to those felt by the aliens. Fortunately, sometimes some actors knew to correct the situation but often, they didn't or didn't care enough to do it. 
