Take a step back and figure out what it is you want to accomplish, and then go from there. You want to ban every semi-automatic firearm? Then figure out the language that is going to cover all of those firearms. But saying "offensive" is a vague and arbitrary term that is just going to get your political opponents to move goal posts and bog you down with irrelevant language. Many people have definitely used an AR-15 as a purely "defensive" weapon in this country. So, saying "offensive" isn't helping your cause.
While I do not support banning all semi-automatic firearms, I'm not going to stand in anyone's way. I also won't sell any firearms that I own back, and I think there is close to zero chance that there is going to be active confiscation of semi-automatic firearms. If, somehow you were to successfully pass a law that called for an active confiscation of all semi-automatic firearms, you can be sure that people will die in that situation at best, and at worse could start the hot civil war that I'd prefer we avoid altogether.
To be clear, I think my political allies should safely own and learn to operate firearms because when the fascists come to murder you in your sleep, the police not only won't be there to protect you, some of them might be there in their civilian clothes or paramilitary uniforms. Anyone who talks about fascism, whether DeSantis or Abbott or any number of current Republicans who have actual power, but then hand-wave away the possibility of fascists doing what fascists do when they have power, are whistling past the graveyard on that one.
You can attempt to ban any and all firearms that you want. I don't think you're going to be successful, and I'm not going to oppose you, but I still believe it's a liberal own-goal. The fascists are still working to overthrow the government. And in case y'all haven't really listened to what the fascists are saying, their trajectory is murdering liberals as their "last stand to defend themselves". That's how fascists always greenlight murdering their fellow citizens.