On the other, it wouldn't be too hard to build some reasonable safeguards into a law like this to protect against obvious abuses while still maintaining the ability for small actors to safely hit back at large ones violating the clear spirit of it.
I think you're glossing over the entire point of why people are concerned. It _would_ be incredibly difficult to add safeguards.
As a side note, you should be aware a Slippery Slope Argument is not necessarily a fallacy. Whether it's a fallacy depends on the strength of the chain of conditions. I'm not normally a Wikipedia fan but their article is reasonably good: https://en.wikipedia.org/wiki/Slippery_slope