Yes it is true that multiple people online may have opposing views on such movements, but these can be beneficial to calling out one's personal bias and learning about different views. Even with groups that are in the wrong, these can be beneficial to the democracy as they help politicians and other people of power to learn insight on opposing views.
Social media is a good resource for movements to keep governments and other oppressive systems in check. This may look like using Twitter to call out the oppressive police system with the hhash-tag #BlackLivesMatter. Weston Gobar's “Social media can be good for democracy” provides evidence in support of this point, "Under the hashtag #BlackLivesMatter, activists were able to share photos and videos of excessive police force and militarization. Not only did activists use Twitter as a platform to publicize the use of tear gas, but activists in Palestine were actually able to provide them with real advice." This shows how activists were able to use social media to impact their governments and make a difference.