No, there are no prohibitions for priests to include these crucial issues in our culture in their homilies at Mass, and thank you for mentioning this. I have been rhetorically asking the same question for decades.
Many Catholics remain either ignorant or unchallenged because they do not hear their priests speaking clearly and persistently on these great evils that permeate our culture; and I would surmise that many fall to the its pressures as a result. Since the devil has led our society through the "sexual revolution" inaugurated by the birth control pill, which I personally call the new fruit of the knowledge of good and evil, parishes have been scandalously silent in combatting the onslaught against the truth of sexuality and human life. It seems like a clear call for us all to shout from the rooftops (Matthew 10:27) Catholic truth.
My advice is to write a note or speak in person to your parish priest about your concerns; writing your local bishops wouldn't hurt either. If you are inclined, there are other ways to help too:
- teach religious education at your parish
- become involved with youth ministry
- get involved with local T.V. and produce a show to educate on these issues
- get a masters degree and teach high school or middle school
- create a website and blog, etc.
I encourage you not to waste the wisdom and inspiration you have been given. The devil will fight you every step of the way because this is his domain, but keep your eyes fixed on Christ (Matthew 14:22-23, 2 Corinthians 1:3-5, Hebrews 12:2) and persevere, and you will do much good.
Without them realizing it, countless lives and souls are counting on Catholics (like you) to say yes to the insight and courage that God has given us. Regarding the inevitable temptations to feel overwhelmed or discouraged, always remember Mother Teresa's wonderful line:
"Christ doesn't call me to be successful, He calls me to be faithful."