Is it bad to lift weights?
I'll try to be a bit more informative....
No, it's not, as long as it's done properly.
To this day, there are many unfounded myths and rumors associated with "progressive resistance training" that have long been proven to be untrue... Yet they persist.
One of the most common, and asked almost daily here on Quora, is "will lifting weights stunt my growth?"
Lots and lots of young men are terribly worried about their height.... No, weight lifting will have no effect whatever on your growth.
Others are that you will become "muscle bound", or "slow", or whatever. For many years, boxers avoided lifting weights because of such fears. All untrue. Essentially, ALL serious athletes do at least some weight training currently, mostly off-season strength training. Even endurance and agility athletes.
Note, you have to differentiate between different types of weight training. "Body building" is mostly concerned with developing a pleasing, symmetrical physique with the greatest amount of "Hypertrophy" possible.
This requires special training methods, special dietary strategies, and lots of time and effort.
You will not develop like a bodybuilder unless you follow a specific bodybuilding training program and dietary regimen.
"Strength training" is what most athletes do... Lifting heavy weights for low repetitions. This does NOT result in great hypertrophy.
Finally, there is "general fitness" training. That's what I do as an old guy. Not interested in athletics or bodybuilding.... Just want to retain strength, muscle mass, and bone health into old age.
You should know that health authorities universally recommend weight training for older folks for this reason.