Same could be said by creationists? Opinions opinions everywhere.
It's not an opinion, it's a theory. Most people have no clue what the definition of theory is, so I'll tell you. A theory is a scientific explanation of observed facts. For instance:
- Over time, organisms are getting more complex
- Organisms adapt in ways that help them in their environment
- Often, similar organisms have similar DNA
- The embryology and anatomy of animals shows similar trends
These are all undeniably true. So, by connecting the dots, we get the theory of evolution. Just because something's a theory doesn't make it less true, or subjective in any way. It just means that it's not a direct fact, which is something you can say yes/no from by looking at data. Let's look at global warming.
- CO2 levels are the highest they've been for all of human history
- CO2 levels have been increasing at a rate higher than ever seen before
- Humans are running processes that output a lot of CO2
- CO2 is proven to create a greenhouse effect that increases temperature
- Global temperatures are rising.
These facts are all undeniably true, proven from many sources. So, if we connect the dots, we get a theory of global warming. Human activity increases CO2 production, CO2 production increases CO2 levels, CO2 increases temperature, and therefore human activity is increasing temperature. There's no opinion here. It's a very solid theory built on undeniable facts. Could it be wrong? Yes, it could. We could find a better explanation in the future. Is it wrong? Not as far as we know. There's no other explanation that can be decently proven, so for all intents and purposes it's correct.