Hi Camila,
Guys that use a threatening photo as their dating profile picture believe that it makes them look tough. They don’t want to come off as though they are weak. The photo with a dead animal is also a sign of their masculinity. They are sending the message that they are protectors and providers. They believe that blatant displays of what they perceive as masculine traits is what attracts women.
When you have swiped right on them in the past and tried to give them advice about the benefit of not having such a threatening dating profile picture, they see that as an attack on their masculinity. That is why they have retorted with telling you that you aren’t that hot.
Yes, something like this can get frustrating. However, being a good Samaritan to guys like this may not be worth your time. Guys like this often need to experience what it is like to get next to no matches on a dating site in order for them to start reassessing the negativity that comes with having a threatening dating profile photo.