So are you saying that your DM just killed your familiar because they dislike familiars? That seems like a bit much, if so.
That's exactly what I'm telling you. I'v met DMs like that, in person and on forums. They think that players are abusing the spell, that they are spotlight hogging, that it gives them (as a DM) extra-work to take care of the familiars not ruining a scenario especially at low level, that it's a bit too much of an easy mode for players, etc.
In the case of my owl-killing DM, it was obviously because there was a kobold ambush cleverly planned and that he did not want us detecting it that easily. The thing is that it did not even work, because the owl disappearance like that actually scared us way more than necessary and we went around and I think avoided it completely anyway. So it did not achieve anything apart from overall frustration.
You know what they say when you assume.
Huh, no, I don't actually, what do they say ?
If what someone says "smacks" of something, but you're not certain, then one way to find out is ask rather than assume the worst and base your arguments on the most uncharitable interpretation.
And that's why we are discussing. I'm perfectly willing to hear that you are absolutely in good faith here, the only thing I'm telling you (and I'm not the only one) is that your "kill on sight" statement puts you - at first glance - squarely in the camp of Familiar-hating-DMs, which is why my (our) suggestion is that you tone it down a bit if it's not what you mean, nothing more.
I can't speak for anyone else's games but my own. In my games, the players are challenged and part of that is threatening their resources when given the opportunity.
And I understand that kind of game, been in them a lot and run them too. It's just that - even though my partner commented yesterday evening that I was possibly a bit harsh with my players

- over the years, some of us have developed a more, let's say, "benevolent" style, where it's less about the challenge and more about simply weaving a tale together without a constant threat. And one reason for that is that some people don't react well when threatened. In particular, a long-time (almost 40 years now) friend of mine - brilliant engineer and manager if a bit shy personally, and in particular excellent chess player - gets into never-ending explanation loops for the simplest of actions so that no-one can think that he made an incorrect decision. Another - same kind of background and personality, unfortunately deceased a few years back - really went into cowardly mode, which caused problems because not only were some people angered by the cowardice, they also taunted him to no end (one even created a character class called the pleutros - french sort of word for coward - with level names like arch-pleutros de la fuite éperdue - something like arch-coward of the never-ending flight), which added to his incomfort as a player. Not nice overall.
So I understand you wanting to present a challenge, and taking every opportunity to destroy player resources when you have the opportunity, but first it's not every kind of game out there, and even then, when doing this, there are many ways to do it, a spectrum from the extremely fair (which I'm perfectly willing to admit is your case) to DMs who actively hunt down every single mistake to punish players, especially in areas that elicit their dislike, for example familiars...