Older male cat problems? Please help!!!?

I recently brought home a small male kitten, he's friendly and curious and he is in no way hard to handle. Problem is, there is a previously wild adult male cat already living in my home and he refuses to accept the new kitten. I brought them together to test the older cat's response, and he began hissing and deeply growling at my new kitten. It scares me to leave them alone together, so I have to consider giving my new kitten away. I just hope I have other options, I want that to be a last resort. Older male is house trained, neutered, and has lived in the house for around a year. So far he has been the only cat in the house along with 3 very large german shepherds. Please, if you can, I need ideas and hopefully a solution to my conundrum. Thank you for your help!