You can help someone if you want. It is not mandatory.
For example, if someone says "RTFM" or "Search Google" to answer another person's question, that is not being helpful. If your intent is to help, then by all means help that person. But unhelpful responses should be withheld and just stay silent.
Just a reminder, you can always ignore someone if you don't want to see their posts again.
Here's how:
If you are on a device with a small screen, click the menu icon first.
On the menu, click Profile > Modify Profile > Buddies/Ignore List > Edit Ignore List. Type in the name of the person you want to ignore and click the Add button. Repeat if you want to add more people to that list.