My K/D is 0.975 right now and I feel I can 'take on' anyone 0.8 or lower quite easily (if we're generalising)
When I see someone above 2 I normally think "They're good, hope they're on my side!" I never assume they must be a camper or a hacker because I've watched people play and I know people are just good. And those who do make these accusations are normally just jealous and don't understand how you could be so good because they already think they're the best.
In other words, those players don't matter. I understand your frustration and maybe it would be nice to choose whether to show your K/D or not, but for now I would just take it as a compliment.
The only person I've ever doubted is someone with a 9.2 K/D but even then I wouldn't accuse them of cheating or anything because it's not impossible. I definitely wouldn't accuse them without even talking to them!
The fact you aren't even on mic emphasises the fact that they are just scared.
Well done on the 3.5. Just ignore them.