Companies brand their products to domains I registered!

I am a novice pretty much to this industry. I have held domains for about 7 or 8 years now. 2 of them companies have branded their product using another extension. I reached out to both and 1 a Canadian company that is publicly traded started in on the lawyer talk. I gave up my name, address etc. I could care less I am not frightened. They are using the .ca extension and I registered the .com prior to their rebranding. The other is a Belguim company and they never responded. My question is, what good is it to think of these brands when others can just go ahead and register another the .net or similar unless of course I trademark but that could get expensive. Also building sites for each is time consuming etc. Thanks if anyone would care to recommend a course of action..