Is it right to learn other martial arts just for the sake of being good at fighting?

Hopefully you are using a bit of hyperbole here and not getting some kind of really severe beatings on testing days. Are you asking if this is right because you know somewhere within, you want to be the one beating students to a pulp? This may cause you to reevaluate your goals and motivations.

Know that no matter how many people you beat up, there will always be others who doubt you and you can't go around beating everyone up.

 

Of course you should cross train if you like your current art but want more. The only other option is to quit your current art and start a new one, which is also ok.

Basically, if you want to be able to fight, then select one of the following arts to augment your training:

• Boxing
• Judo
• Wrestling
• Muay Thai
• BJJ

Keep in mind this list is not exhaustive, just a sampling. You might also look to training MMA for a well-rounded skill set. Unless you're in an isolated area, finding something appropriate should be relatively easy. What's your current art?

 

Yoseikan budō - Wikipedia

It's Yoseikan, so they usually do a far bit of sparring, it's inbuilt into the system.