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From a practical perspective, it interferes with getting your point across to overload a symbol that already has strong associations. From a social perspective, it's considerate not to use symbols that have strong negative associations for others (which is not a view shared by the "fuck your feelings" crowd, although I've noticed that they're not all that consistent in that view, and it tends to depend on whose feelings are getting fucked.)
Triangles are the most basic shape available so you'll find any and all kinds of symbols to represent good and bad things. I don't think it's very productive to worry about how it was used 70 years ago unless you're talking to a very old person.
Like I said, I'm not telling anyone what to do. Everyone can feel free to call anything whatever they want, to use or reuse symbols as they see fit. The signifier is not the signified.
Just wanted people to know. Because like I said, if your goal is to communicate, you might want to know if you're using something that has another, emotionally-loaded interpretation.