Though there is a distinction between corporate lobbying and e.g. the EFF: corporations lobby for their own interests, the EFF does it for everyone. Besides that, if company lobbying did not exist, the EFF wouldnt exist because there would be no one to work against. The EFF was specificly founded to defend the peoples interests against corporations.
You need to be more pedantic. The EFF is a 501(c)(3) organization, and that's a type of corporation.
If you want to outlaw lobbying by for-profit corporations, then they'll just create subsidiary lobbying organizations. The NRA is a 501(c)(4), which is also a tax exempt non-profit designation, and realistically it serves primarily as a lobbying group for gun manufacturers.
That's a fair point. Though while they may not be exclusively a lobbying front for gun manufacturers, I think it's still fair to say they serve that purpose.