It's okay, even encouraged, for you to have a different opinion. Form your own thoughts, figure out what is and is not okay with you, and voice those feelings out loud! Just, please, beware of who you're talking to, how your wording your opinion, and your tone of voice. Sometimes, if you feel very strongly about a subject, you speak passionately about that subject, but try to remember that, if you don't watch your tone of voice, you're passion may be mistaken for anger. We're human, we all won't agree on everything, and we don't have to. Just be careful.
I will be the first to admit that I sometimes have a problem with this. My parents and I often talk about controversial subjects, and, although a majority of the time we agree, sometimes they will look at me with a funny expression and basically tell me to calm down. If it weren't for their gentle and joking reminders to watch my tone when I feel passionate about something, I wouldn't know how to respectfully disagree with someone. Respect is the key on having a debate, or even just a serious conversation.
Most importantly, remember to take into account that the person you're disagreeing with may feel just as strongly about the opposite side of the argument as you do your side of the argument. Think about how you would feel if someone came at you in the same tone of voice or with the same wording that you're using from the opposite side of the argument, and whether you would be offended with how they are speaking to you. It's easy to turn a controversial subject into something that degrades and disrespects the person you're talking to. This is why things like politics are such touchy subjects.
This isn't something to remember for only an in person conversation. With the upcoming election looming over our heads, it's becoming more and more common to see people posting their political opinions online. It's okay to do this, just, again, be careful. Whether you're replying to someone else's post or making your own post, you have to take into account how your message is going to be perceived. Everything posted on social media is public, so using the argument, "It's on my personal page, I can say what I want," is irrelevant when taking into account another's feelings. Posting something online automatically makes it an open discussion, and it's essential to be aware of that.
I'm not saying to stop voicing your opinions. I'm actually encouraging it. I want you to be controversial. Just remember that you will come off more intelligent and more considerate if you are able to recognize that there is a difference in disagreeing and disrespecting. The moment you are able to respectfully disagree is the moment you become an effective debater.