As Speaker of the House, Paul Ryan has little choice but to endorse Trump in order to try to gain some party unity. I think if wasn't speaker he would not have made the endorsement, but as the Republican leader one of his responsibilities is to help the party win up and down the ticket.
House Speaker Paul Ryan is being forced to endorse Donald Trump for president. Ryan has long been a critic of Trump's style on the campaign trail. Trump's bombastic and offensive comments continue to spark controversy in many quarters of the electorate. Ryan feels like its his job to apologize on behalf of the Republican Party. However, it would be unprecedented for Ryan not to endorse the Republican presidential candidate. Therefore, Ryan feels like he has no choice but to support Trump.
No, Paul Ryan is not being forced into endorsing Trump just because he is a republican. Many republicans in office have publicly denounced the candidate and although they, and Ryan, may face scrutiny by the republican party, they have free will to endorse a candidate of their choice, especially when they oppose Trump's rhetoric and ideas.
Paul Ryan is not being forced into anything. He's an adult who's capable of making his own choices, so he can endorse whoever he wants. There is most likely a lot of political pressure for him to support Trump, especially since he is running for re-election. However, he doesn't have to give into this. If he doesn't like Trump (and it seems pretty clear that he doesn't), he shouldn't endorse him.