ANSWER:

No you are not sinful and you are not disobedient. What you said was right. 

Handle this matter with respect and diplomatically try to resolve this matter by giving them some other option of gifting to your groom which will benefit both of you in future. If your husband to be is a practicing muslim, he will not wear and would sell it and use the money. Therefore, don’t make a scene out of it. 

Sir my parents said they will gift a gold ring as dowry to my groom,here in india dowry is must and i denied that coz gold is haram on men,a man wearing gold on wedding is more worse for me ,i denied, my mom said me dnt bring saudi law here its india,and saying m disobedient child, am i? For saying No to haram? does it make me a bad child? My mom also tortured me for saying no, i follow Allahs law