As I said, I think the primary things for me were the professional concerns about jobs being lost and Canadian skills disappearing, but on a personal level there are many things that deeply disturb me about ATK. I don't think it is fair to just say it is the same as another large American weapons manufacturer. They are not all the same.
ATK builds land mines. ATK builds cluster munitions, which presumably will soon be banned or potentially will soon be banned. They build depleted uranium rounds; they're the largest producer in the U.S. of depleted uranium rounds. They are a major contractor involved in missile defence activities. In particular, ATK was a major contractor on the missile that was used to shoot down the satellite a few weeks ago.
The range of activities they're involved in is quite amazing. They've built an airburst assault rifle for shooting around corners. There are a number of things that ethically are extremely questionable.